Fix Repo field

[dr3dd589]

changed Repo model to URLField from CharField.
DB migration file added.

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• Your code is flake8 compliant (DefectDojo's code isn't currently flake8 compliant, but we're trying to correct that.)
• If this is a new feature and not a bug fix, you've included the proper documentation in the ReadTheDocs documentation folder. https://github.com/DefectDojo/Documentation/tree/master/docs or provide feature documentation in the PR.
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• Add applicable tests to the unit tests.

[valentijnscholten]

What if the existing data in this column contains data that doesn't pass the https://docs.djangoproject.com/en/2.2/ref/validators/#django.core.validators.URLValidator used by the URLField? Or are there other checks in DD which should have prevented this already?

[dr3dd589]

hello, @valentijnscholten I have tested it locally and it does not affect on existing data that does not validate URLValidator rule.