Support for Strings Catalogs (Xcode 15) (#1421)

* Support for xcode 15 string catalogs

* Add sample string catalog to Test Fixture and basic test to check that asset catalogs are added in the resources build phase

* Restore unintended changes

* Update Pull Request number for 'Support for Strings Catalogs' in changelog

* Update fixture yml generator

* Detect knownRegions based on locales in string catalogs

Sources/XcodeGenKit/StringCatalogDecoding.swift

@@ -0,0 +1,82 @@
+import Foundation
+import JSONUtilities
+import PathKit
+
+struct StringCatalog {
+    
+/**
+*       Sample string catalog:
+     
+*     {
+*        "sourceLanguage" : "en",
+*        "strings" : {
+*            "foo" : {
+*                "localizations" : {
+*                    "en" : {
+*                        ...
+*                    },
+*                    "es" : {
+*                        ...
+*                    },
+*                    "it" : {
+*                        ...
+*                    }
+*                }
+*            }
+*        }
+*     }
+*/
+    
+    private struct CatalogItem {
+        private enum JSONKeys: String {
+            case localizations
+        }
+        
+        private let key: String
+        let locales: Set<String>
+        
+        init?(key: String, from jsonDictionary: JSONDictionary) {
+            guard let localizations = jsonDictionary[JSONKeys.localizations.rawValue] as? JSONDictionary else {
+                return nil
+            }
+            
+            self.key = key
+            self.locales = Set(localizations.keys)
+        }
+    }
+    
+    private enum JSONKeys: String {
+        case strings
+    }
+    
+    private let strings: [CatalogItem]
+    
+    init?(from path: Path) {
+        guard let catalogDictionary = try? JSONDictionary.from(url: path.url),
+              let catalog = StringCatalog(from: catalogDictionary) else {
+            return nil
+        }
+        
+        self = catalog
+    }
+    
+    private init?(from jsonDictionary: JSONDictionary) {
+        guard let stringsDictionary = jsonDictionary[JSONKeys.strings.rawValue] as? JSONDictionary else {
+            return nil
+        }
+
+        self.strings = stringsDictionary.compactMap { key, value -> CatalogItem? in
+            guard let stringDictionary = value as? JSONDictionary else {
+                return nil
+            }
+            
+            return CatalogItem(key: key, from: stringDictionary)
+        }
+    }
+    
+    var includedLocales: Set<String> {
+        strings.reduce(Set<String>(), { partialResult, catalogItem in
+            partialResult.union(catalogItem.locales)
+        })
+    }
+}