Added the Utility package (#29)

This PR contains the work done to create the new **Utility** package within the project, and also included in it the `NormalizeEmail` method, as it's not something that belongs to the **Infrastructure** package.

Reviewed-on: rock-n-code/loud-amsterdam#29
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>

Packages/Utility/README.md

@@ -0,0 +1,31 @@
+# Utility
+The general-purpose helpers the **Loud** services share: small, single-purpose methods with no dependencies beyond Foundation and no ties to any web framework.
+
+## Overview
+The package provides, grouped by role:
+| Role | Types |
+| --- | --- |
+| Validation | `NormalizeEmail`, which reduces a submitted email address to its canonical form |
+
+## Design rules
+- **Dependency-free.** A helper belongs here only while it needs nothing beyond Foundation; one that grows a framework dependency belongs in the package owning that framework's concerns (e.g. `Infrastructure` for Hummingbird).
+- **Method structs.** Helpers hold their lifetime-fixed configuration in `init` and take only per-call inputs in `callAsFunction`.
+
+## Layout
+Sources are split by visibility, then by kind, one type per file:
+```
+Sources/
+└── Public/
+    └── Methods/           NormalizeEmail
+Tests/
+├── Cases/                 the test suites, mirroring the Sources/ layout
+└── Utils/                 the suite Tag constants
+```
+
+## Testing
+Every suite carries a tag naming the kind of API it exercises — `.method`, declared in `Tests/Utils/Extensions/Tag+Constants.swift` — so test plans and result summaries can slice the run by kind. A new suite must adopt the tag matching its subject (or add a tag there if none fits).
+
+## Requirements
+- Swift 6.3 toolchain (`swift-tools-version:6.3`).
+- macOS 15, matching the sibling `Infrastructure`, `Localization`, and `Persistence` packages (the services deploy to Linux containers; the packages carry no UI platforms).
+- No package dependencies — Foundation only.