Add todos for Entity Id and type. Add example usage of OpenAPI entity schema support in Playground

JSONAPI.playground/Pages/OpenAPI Documentation.xcplaygroundpage/Contents.swift

@@ -0,0 +1,13 @@
+//: [Previous](@previous)
+
+import Foundation
+import JSONAPI
+import JSONAPIOpenAPI
+
+// print Entity Schema
+let encoder = JSONEncoder()
+encoder.outputFormatting = .prettyPrinted
+
+let personSchemaData = try? encoder.encode(Person.openAPINode())
+
+print(personSchemaData.map { String(data: $0, encoding: .utf8)! } ?? "Schema Construction Failed")

JSONAPI.playground/Sources/OpenAPISupport.swift

@@ -0,0 +1,16 @@
+import Foundation
+import JSONAPI
+import JSONAPITesting // for the convenience of literal initialization
+import JSONAPIOpenAPI
+
+extension PersonDescription.Attributes: Sampleable {
+	public static var sample: PersonDescription.Attributes {
+		return .init(name: ["Abbie", "Eibba"], favoriteColor: "Blue")
+	}
+}
+
+extension PersonDescription.Relationships: Sampleable {
+	public static var sample: PersonDescription.Relationships {
+		return .init(friends: ["1", "2"], dogs: ["2"], home: "1")
+	}
+}

JSONAPI.playground/contents.xcplayground

@@ -3,5 +3,8 @@
     <pages>
         <page name='Test Library'/>
         <page name='Usage'/>
+        <page name='Full Client &amp; Server Example'/>
+        <page name='Full Document Verbose Generation'/>
+        <page name='OpenAPI Documentation'/>
     </pages>
 </playground>