Invalid Argument errors provide per field details. (#110)

* Invalid Argument errors now return a per field error message.

* Creating an API error struct.

* SDK uses field error details proto.

* Adding tests specifically for handler helper error messages resulting in expected API output.

* Inlining the error checks into the table driven tests.  Use protocmp for assertions to make printing out diffs easier to parse.

* Aggregate the invalid argument fields detected to be wrong.

* Make the returned order of fields deterministic in the error details..

* Fixing formatting issue in errors_test.go.

* Test to confirm unimplemented results in a 405 and not 404.

api/internal/genapi/input.go

@@ -37,6 +37,17 @@ var inputStructs = []*structInfo{
 		"",
 		templateTypeResource,
 	},
+	{
+		os.Getenv("GEN_BASEPATH") + "/internal/gen/controller/api/error.pb.go",
+		"FieldError",
+		os.Getenv("GEN_BASEPATH") + "/api/field_error.gen.go",
+		"FieldError",
+		"api",
+		"",
+		"",
+		"",
+		templateTypeResource,
+	},
 	{
 		os.Getenv("GEN_BASEPATH") + "/internal/gen/controller/api/resources/hosts/host.pb.go",
 		"Host",