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>

Services/Website/Sources/App/App.swift

@@ -2,8 +2,17 @@ import Configuration
 import Hummingbird
 import Logging
 
+/// The entry point of the website executable.
+///
+/// Loads the configuration, then either serves the website or — when the `database.migrate` flag is set — runs the registered migrations against the
+/// configured backend and exits.
 @main
 struct App {
+
+    /// Loads the configuration and runs the mode it selects.
+    ///
+    /// The configuration is read from the providers in precedence order: command-line arguments first, then process environment variables, then a
+    /// `.env` file when one is present, and finally the in-memory defaults (currently just the server name).
     static func main() async throws {
         let reader = try await ConfigReader(
             providers: [
@@ -19,10 +28,22 @@ struct App {
             ]
         )
 
+        // Migrate-and-exit mode runs the registered migrations against the configured backend and returns,
+        // so a shared database is migrated by a single deliberate invocation (`--database-migrate`) rather
+        // than by every booting instance.
+        guard !reader.migrate else {
+            try await migration(
+                reader: reader
+            )
+
+            return
+        }
+
         let app = await application(
             reader: reader
         )
 
         try await app.runService()
     }
+
 }