feat: Add codable identifier arrays (#15)

Sources/KituraContracts/ClosureAliases.swift

@@ -31,6 +31,11 @@ The `CodableArrayResultClosure` is used by other `Codable` aliases when respondi
 */
 public typealias CodableArrayResultClosure<O: Codable> = ([O]?, RequestError?) -> Void
 
+/**
+ The `IdentifierCodableArrayResultClosure` is used by other `Codable` aliases when responding with an array of tuples containing an identifier and a Codable object, or an `RequestError`.
+ */
+public typealias IdentifierCodableArrayResultClosure<Id: Identifier, O: Codable> = ([(Id, O)]?, RequestError?) -> Void
+
 /**
 The `IdentifierCodableResultClosure` is used by other `Codable` aliases when responding with an object which conforms to Codable and/or an object that conforms to `Identifier` or `RequestError` is needed.
 */
@@ -202,6 +207,31 @@ router.get("/users") { (respondWith: ([User]?, RequestError?) -> Void) in
 */
 public typealias CodableArrayClosure<O: Codable> = (@escaping CodableArrayResultClosure<O>) -> Void
 
+/**
+ The `IdentifierCodableArrayClosure` is for use in cases where you'd want to perform a series of actions then respond with an array of tuples containing an identifier and a Codable object, or an `RequestError`, in the form of a `IdentifierCodableArrayResultClosure`.
+
+ ### Usage Example: ###
+ ````
+ router.get("/users") { (respondWith: ([(Int, User)]?, RequestError?) -> Void) in
+     if databaseConnectionIsOk {
+
+         ...
+
+         //If no errors occured and you have an array of Users you can just respond with the users by passing nil as the 'RequestError?' value.
+        respondWith([(Int, User)], nil)
+
+     } else {
+
+         ...
+
+         //If there has been an error you can use the respondWith call to respond with an appropiate error and passing nil for the [User]?.
+         respondWith(nil, .internalServerError)
+     }
+ }
+ ````
+ */
+public typealias IdentifierCodableArrayClosure<Id: Identifier, O: Codable> = (@escaping IdentifierCodableArrayResultClosure<Id, O>) -> Void
+
 /**
 The `SimpleCodableClosure` is for use in cases where you'd want to perform a series of actions then respond with an object conforming to `Codable` or a `RequestError` in the form of a `CodableResultClosure`.