Marshmallow schema and field updates for PID and other helpers

[ppanero]

Fixes: https://github.com/inveniosoftware/invenio-records-rest/issues/232 Fixes: cookiecutter-invenio-instance#97 In order to use it the loader should be overwritten with:

record_loaders={
            'application/json': ('invenio_records_rest.loaders:json_pid_checker')
        },

And add the PID attribute name on the environment / config file:

[ INVENIO_ ]RECORDS_REST_PID_ATTR_NAME = 'control_number'

For the code:

• Should the "get_pid" function be customizable (e.g. through import_string())? If not, is json.py the best place to be for this function, utils.py?
• There is a test file for custom marshmallow loaders. Should it be overwritten? Should I create a new one? Mainly to comply with coveralls.

For the tests:

• Create record (post), chek record PID.
• Update with wrong PID, check it does not change (search + DB)
• Update with no PID, check it does not change (search + DB)

Small punctualization: In order to follow the naming convention of this repo/other invenio repos, shouldn't the file be named test_loader_marshmallow instead of test_marshmallow_loader (e.g. check the serializers).

[ppanero]

@slint The changes are missing the tests:

• Test the new RecordMetadataSchemaJSONV1 in order to check proper RECID_FIELD value injection.
• Cross check the test_marshmallow_load in test_marshmallow_loader.py. Since the serializer is not declared the following assertion will never be correct:

      assert 'pid' in data_dump.data.get('metadata')

• Create a test to check the serialization with the PersistentIdentifier field.

Lastly and for consistency the name of ``test_marshmallow_loader.py should be changed to test_loader_marshmallow.py.

Code has been tested manually in my application and works as desired.

[slint]

I would say, let's postpone until https://github.com/inveniosoftware/cookiecutter-invenio-instance/pull/92 is merged, so that it's tested on the cookiecutter-invenio-instance as well

[ppanero]

@slint the cookiecutter PR has been merged, I am going to test it. Just that I cannot put myself as a reviewer :rofl:

[ppanero]

Tested. Also closes https://github.com/inveniosoftware/cookiecutter-invenio-instance/issues/97