Add some convenience initializers for the most basic success and error documents

Author: mattpolzin

Sources/JSONAPI/Document/Document.swift

@@ -655,3 +655,37 @@ extension Document.SuccessDocument where IncludeType: _Poly1 {
         }
     }
 }
+
+extension Document where MetaType == NoMetadata, LinksType == NoLinks, IncludeType == NoIncludes, APIDescription == NoAPIDescription {
+    public init(body: PrimaryResourceBody) {
+        self.init(
+            apiDescription: .none,
+            body: body,
+            includes: .none,
+            meta: .none,
+            links: .none
+        )
+    }
+
+    public init(errors: [Error]) {
+        self.init(apiDescription: .none, errors: errors)
+    }
+}
+
+extension Document.SuccessDocument where Document.MetaType == NoMetadata, Document.LinksType == NoLinks, Document.IncludeType == NoIncludes, Document.APIDescription == NoAPIDescription {
+    public init(body: PrimaryResourceBody) {
+        self.init(
+            apiDescription: .none,
+            body: body,
+            includes: .none,
+            meta: .none,
+            links: .none
+        )
+    }
+}
+
+extension Document.ErrorDocument where Document.MetaType == NoMetadata, Document.LinksType == NoLinks, Document.IncludeType == NoIncludes, Document.APIDescription == NoAPIDescription {
+    public init(errors: [Error]) {
+        self.init(apiDescription: .none, errors: errors)
+    }
+}

Tests/JSONAPITests/Document/DocumentTests.swift

@@ -39,6 +39,28 @@ class DocumentTests: XCTestCase {
                 links: .none
         ))
 
+        test(JSONAPI.Document<
+            NoResourceBody,
+            NoMetadata,
+            NoLinks,
+            NoIncludes,
+            NoAPIDescription,
+            UnknownJSONAPIError
+            >(
+                body: .none
+        ))
+
+        test(JSONAPI.Document<
+            NoResourceBody,
+            NoMetadata,
+            NoLinks,
+            NoIncludes,
+            NoAPIDescription,
+            UnknownJSONAPIError
+            >(
+                errors: []
+        ))
+
         // Document.SuccessDocument
         test(JSONAPI.Document<
             NoResourceBody,
@@ -55,6 +77,17 @@ class DocumentTests: XCTestCase {
                 links: .none
         ))
 
+        test(JSONAPI.Document<
+            NoResourceBody,
+            NoMetadata,
+            NoLinks,
+            NoIncludes,
+            NoAPIDescription,
+            UnknownJSONAPIError
+            >.SuccessDocument(
+                body: .none
+        ))
+
         // Document.ErrorDocument
         test(JSONAPI.Document<
             NoResourceBody,
@@ -67,6 +100,17 @@ class DocumentTests: XCTestCase {
                 apiDescription: .none,
                 errors: []
         ))
+
+        test(JSONAPI.Document<
+            NoResourceBody,
+            NoMetadata,
+            NoLinks,
+            NoIncludes,
+            NoAPIDescription,
+            UnknownJSONAPIError
+            >.ErrorDocument(
+                errors: []
+        ))
     }
 
 	func test_singleDocumentNull() {