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/Package.swift

@@ -23,6 +23,9 @@ let package = Package(
         .package(
             path: "../../Packages/Localization"
         ),
+        .package(
+            path: "../../Packages/Persistence"
+        ),
         .package(
             url: "https://github.com/elementary-swift/elementary.git",
             from: "0.6.0"
@@ -52,6 +55,7 @@ let package = Package(
         .executableTarget(
             name: "Website",
             dependencies: [
+                .byName(name: "Persistence"),
                 .byName(name: "WebsiteCore"),
                 .product(
                     name: "Configuration",
@@ -72,6 +76,7 @@ let package = Package(
             name: "WebsiteCore",
             dependencies: [
                 .byName(name: "Localization"),
+                .byName(name: "Persistence"),
                 .product(
                     name: "Configuration",
                     package: "swift-configuration"