add set_user_name() and set_user_email() api to the repository class

### actual behavior:
the default username and email is None, without and endpoint in the repository class to change them

### desired behavior:
create set_user_name(), set_user_email() methods to perform this task

### reference:
https://github.com/abdelwahabram/shed/blob/64110a4761b9d239fbe348737a355f122a463b71/source/repository.py#L8C1-L8C6

Look at the repository.py file, specifically lines 8-6 referenced in the issue. The default username and email are currently None. Add set_user_name() and set_user_email() methods to the Repository class. Check for existing tests or create a simple test to verify the methods update the attributes correctly.

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