Fixes for the Localization package (#26)

This PR contains the work done to

Reviewed-on: rock-n-code/loud-amsterdam#26
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Packages/Localization/Tests/Cases/Public/Methods/NegotiateTests.swift

@@ -26,6 +26,20 @@ struct NegotiateTests {
         #expect(language == "de")
     }
 
+    @Test
+    func `matches a regional catalog language exactly`() {
+        let language = negotiate(acceptLanguage: "pt-BR")
+
+        #expect(language == "pt-BR")
+    }
+
+    @Test
+    func `matches a regional catalog language by its primary subtag`() {
+        let language = negotiate(acceptLanguage: "pt")
+
+        #expect(language == "pt-BR")
+    }
+
     @Test
     func `respects the header order of preference`() {
         let language = negotiate(acceptLanguage: "de, en")
@@ -34,12 +48,47 @@ struct NegotiateTests {
     }
 
     @Test
-    func `strips quality weights from the language tags`() {
-        let language = negotiate(acceptLanguage: "de;q=0.5, en;q=0.9")
+    func `orders the language tags by descending quality weight`() {
+        let language = negotiate(acceptLanguage: "en;q=0.5, de;q=0.9")
 
         #expect(language == "de")
     }
 
+    @Test
+    func `treats a tag without a weight as the highest preference`() {
+        let language = negotiate(acceptLanguage: "en;q=0.9, de")
+
+        #expect(language == "de")
+    }
+
+    @Test
+    func `treats a tag with a malformed weight as the highest preference`() {
+        let language = negotiate(acceptLanguage: "en;q=0.9, de;q=broken")
+
+        #expect(language == "de")
+    }
+
+    @Test
+    func `drops language tags weighted as not acceptable`() {
+        let language = negotiate(acceptLanguage: "de;q=0, en;q=0.8")
+
+        #expect(language == "en")
+    }
+
+    @Test
+    func `falls back to the default when every tag is weighted as not acceptable`() {
+        let language = negotiate(acceptLanguage: "de;q=0, fr;q=0")
+
+        #expect(language == "en")
+    }
+
+    @Test
+    func `serves the default language for a wildcard`() {
+        let language = negotiate(acceptLanguage: "fr;q=0.9, *;q=0.5")
+
+        #expect(language == "en")
+    }
+
     @Test
     func `trims whitespace around the language tags`() {
         let language = negotiate(acceptLanguage: " de , en ")