feat: UUID extended to conform to Identifier (#47)

Sources/KituraContracts/Contracts.swift

@@ -963,6 +963,23 @@ extension Bool: Identifier {
     }
 }
 
+extension UUID: Identifier {
+    /// Creates a UUID identifier from a given string representation.
+    /// - Throws: An `IdentifierError.invalidValue` if the given string cannot be converted to a UUID.
+    public init(value: String) throws {
+        if let id = UUID(uuidString: value) {
+            self = id
+        } else {
+            throw IdentifierError.invalidValue
+        }
+    }
+
+    /// The string representation of the identifier.
+    public var value: String {
+        return self.uuidString
+    }
+}
+
 /**
   An enum containing the ordering information
   ### Usage Example: ###

Tests/KituraContractsTests/KituraContractsTests.swift

@@ -72,6 +72,25 @@ class KituraContractsTests: XCTestCase {
         XCTAssertEqual(123456,  intIdentifier)
     }
 
+    // Test UUID conforms to Identifier
+    func testUUIDIdentifier() {
+        let uuidStr = "12345678-1234-4000-ABCD-BA9876543210"
+        guard let identifier: Identifier = try? UUID(value: uuidStr) else {
+            XCTFail("Failed to create a UUID identifier!")
+            return
+        }
+        XCTAssertEqual(uuidStr,  identifier.value)
+
+        guard let uuidIdentifier = identifier as? UUID else {
+            XCTFail("Failed to cast to concrete type: UUID")
+            return
+        }
+        XCTAssertEqual(UUID(uuidString: uuidStr), uuidIdentifier)
+
+        let bogusUUIDStr = "NOPE"
+        XCTAssertThrowsError(try UUID(value: bogusUUIDStr), "Failed to throw with bogus UUID value")
+    }
+
 //    func testTypeComputation() {
 //        XCTAssertEqual(User.type, "User")
 //        XCTAssertEqual(User.typeLowerCased, "user")