Add runpython script to add missing default fields

[JacquelineMorrissette]

Checklist

1. If you've added code that should be tested, add tests
2. If you've changed APIs, update (or create!) the documentation
3. Ensure the tests pass
4. Make sure that your code lints and that you've followed our coding style
5. Write a description of your work suitable for publishing on our forum
6. Mention any related issues in this repository (as #ISSUE) and in other repositories (as kobotoolbox/other#ISSUE)
7. Open an issue in the docs if there are UI/UX changes

Description

Add a RunPython script to add the missing full_name and description to Constance USER_METADATA_FIELDS and PROJECT_METADATA_FIELDS if the fields are missing

[JacquelineMorrissette]

@noliveleger I'm not sure what's going on with the tests, everything is passing locally but all tests in github have errors

[noliveleger]

@noliveleger I'm not sure what's going on with the tests, everything is passing locally but all tests in github have errors

@JacquelineMorrissette , I guess your branch is not up-to-date locally and you did not bring latest changes of the parent branch (feature/user-project-metadata) in your branch.
Please, have a look at my comment in your other PR (if it's not done already) ;-)

Long story short: The main problem is because of the use of json.loads() vs to_python_objects() and json.dumps() vs LazyJSONSerializable() for Constance attributes.