[API] Read default value field option and ensure it matches field type

[jasmine-wu-ai]

Add a field option default_value of type google.protobuf.Value (already done in applied2). Set the default value in the jsonschema if it matches the expected type, if not throw error.

Tests:

• added a new test
• unsure how to add an "assertThrows" test to validate that when the type and value don't match there is an error thrown, but did manually test.