Database setup for the Website service (#13)

This PR contains the work done to introduce a _Fluent_-based persistence layer for the Website service, selectable at runtime alongside the existing in-memory default, plus the local dev tooling and docs to support it.

To provide further details about the work:

* Persistence package
  * The `Driver` and `TLS` enumerations
  * The `Configuration` type
  * The `Service` factory that builds the  service
  * `PrepareDB` for migrations registration
  * The `Probe` for readiness checks.

* App integration
  *  Builds the driver, registers migrations, and attaches `Fluent` to the service lifecycle so it starts/stops with the HTTP server.
  * Migrate-on-boot is gated to the in-memory backend; MySQL/MariaDB is migrated out of band via --database-migrate so shared databases never race on startup.
  * The `ConfigReader+Properties` extension maps database.* config keys onto the driver.

* Library
  * Added database configuration constants.
  * The `HealthController` controller gains a readiness probe: `GET /health/ready` checks whether the database is reachable, separate from the existing liveness check.

* Others
  * Updated the `docker-compose` files to support a database service behind a database profile, and hardened for local development
  * New database targets on the `Makefile` file and overall documentation updated
  * Updated the `.env.local`, `Dockerfile`, and `README` files to document the persistence workflow, config keys, and local DB commands

Reviewed-on: rock-n-code/loud-amsterdam#13
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Packages/Persistence/Sources/Public/Methods/PrepareDB.swift

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+import HummingbirdFluent
+
+/// A registrar declaring every migration against a `Fluent` service.
+///
+/// Built once around the application's `Fluent` service and called as a function — `await migrate()` —
+/// during startup, before the migrations are applied.
+public struct PrepareDB {
+
+    // MARK: Initializers
+
+    /// Creates a registrar for the migrations for a `Fluent` service.
+    public init() {}
+
+    // MARK: Methods
+
+    /// Registers every migration against the `Fluent` service, in order.
+    ///
+    /// This is the single place migrations are declared: add each new migration here, in the order it must
+    /// run (migrations are applied in registration order and are append-only). Registering does not apply
+    /// them — the caller runs `fluent.migrate()` (or the executable's migrate-and-exit mode) to do that.
+    public func callAsFunction(
+        for fluent: Fluent
+    ) async {
+        await fluent.migrations.add([
+            CreateExampleRecord()
+        ])
+    }
+
+}

Packages/Persistence/Sources/Public/Methods/Probe.swift

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+import HummingbirdFluent
+import SQLKit
+
+/// A readiness probe reporting whether the database behind a `Fluent` service is reachable.
+///
+/// Built once around the application's `Fluent` service and called as a function whenever a fresh
+/// answer is needed — typically from a readiness endpoint: `let ready = await probe()`.
+public struct Probe: Sendable {
+
+    // MARK: Properties
+
+    /// The `Fluent` service whose default database is probed.
+    private let fluent: Fluent
+
+    // MARK: Initializers
+
+    /// Creates a probe for the default database of the given `Fluent` service.
+    /// - Parameter fluent: the `Fluent` service whose default database is probed.
+    public init(
+        fluent: Fluent
+    ) {
+        self.fluent = fluent
+    }
+
+    // MARK: Methods
+
+    /// Reports whether the database behind the `Fluent` service is reachable.
+    ///
+    /// Runs a trivial `SELECT 1` against the default database — the cheapest statement both the MySQL/MariaDB
+    /// and SQLite backends understand — so a readiness check does not depend on any particular schema or model.
+    /// Any failure (connection refused, authentication error, pool exhausted) is reported as not reachable
+    /// rather than thrown, so callers can map it straight onto a readiness response. A default database that
+    /// is not an SQL database is likewise reported as not reachable.
+    /// - Returns: `true` when the database answers the probe, `false` otherwise.
+    public func callAsFunction() async -> Bool {
+        guard let database = fluent.db() as? any SQLDatabase else {
+            return false
+        }
+        
+        do {
+            try await database.raw("SELECT 1").run()
+            
+            return true
+        } catch {
+            return false
+        }
+
+    }
+}

Packages/Persistence/Sources/Public/Methods/Service.swift

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+import FluentMySQLDriver
+import FluentSQLiteDriver
+import HummingbirdFluent
+import Logging
+
+/// A factory building the `Fluent` service the application persists through.
+///
+/// Built once around the driver the executable picks at startup and called as a function to produce
+/// the configured service: `let fluent = service()`.
+public struct Service: Sendable {
+
+    // MARK: Properties
+
+    /// The persistence backend to register.
+    private let driver: Driver
+
+    /// The logger the database emits through.
+    private let logger: Logger
+
+    // MARK: Initializers
+
+    /// Creates a factory for a `Fluent` service backed by the given driver.
+    /// - Parameters:
+    ///   - driver: the persistence backend to register.
+    ///   - logger: the logger the database emits through.
+    public init(
+        driver: Driver,
+        logger: Logger
+    ) {
+        self.driver = driver
+        self.logger = logger
+    }
+
+    // MARK: Methods
+
+    /// Builds a `Fluent` service configured for the driver.
+    ///
+    /// The selected backend is registered as the *default* database, so repositories resolve it with a plain
+    /// `fluent.db()` and stay agnostic of which driver is in use. The returned service is not yet running; add
+    /// it to the application's service group (`app.addServices(_:)`) so it starts and shuts its connection pool
+    /// down alongside the server.
+    /// - Returns: the configured `Fluent` service, ready to be added to the service group.
+    public func callAsFunction() -> Fluent {
+        let fluent = Fluent(
+            logger: logger
+        )
+
+        switch driver {
+        case .mysql(let configuration):
+            fluent.databases.use(
+                .mysql(
+                    configuration: .init(
+                        hostname: configuration.host,
+                        port: configuration.port,
+                        username: configuration.username,
+                        password: configuration.password,
+                        database: configuration.name,
+                        tlsConfiguration: configuration.tls.tlsConfiguration
+                    ),
+                    maxConnectionsPerEventLoop: configuration.maxConnectionsPerEventLoop
+                ),
+                as: .mysql,
+                isDefault: true
+            )
+        case .inMemory:
+            // A single connection keeps every query pointed at the same in-memory store,
+            // rather than each pooled connection getting its own private database.
+            fluent.databases.use(
+                .sqlite(.memory, maxConnectionsPerEventLoop: 1),
+                as: .sqlite,
+                isDefault: true
+            )
+        }
+
+        return fluent
+    }
+
+}