Tweaks and fixes throughout the project (#27)

This PR contains the work done to do a little bit of housekeeping pass across all packages and the Website service.

To provide further details about the work:
* Refreshed the READMEs and source documentation to match the current code;
* Tagged every test case consistently across the Infrastructure, Localization, Persistence, and Website test targets;
* Removed Website middleware tests now covered by Infrastructure's own suite;
* Conformed the `PrepareDB` method to Sendable;
* Relaxes the production Compose DATABASE_TLS default from require to prefer;
* Added Persistence test verifying the prefer posture falls back to plaintext connections.

Reviewed-on: rock-n-code/loud-amsterdam#27
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Packages/Localization/Tests/Utils/Extensions/Tag+Constants.swift

@@ -0,0 +1,8 @@
+import Testing
+
+extension Tag {
+    /// Tests exercising a method of the Localization package.
+    @Tag static var method: Tag
+    /// Tests exercising a type of the Localization package.
+    @Tag static var type: Tag
+}