Drop username from user and replace it with uid

...s/83a3a47a6351_add_username_and_display_name_and_drop_.py

alembic/versions/9fa582febebe_delete_username_from_user.py

alembic/versions/cafa1e01b782_create_permission_table.py

app/api/dependencies.py

app/api/endpoints/bucket_permissions.py

app/api/endpoints/buckets.py

app/api/endpoints/login.py

app/api/endpoints/users.py

app/crud/crud_bucket.py

app/crud/crud_bucket_permission.py

app/crud/crud_user.py

app/models/user.py

app/schemas/bucket.py

app/schemas/bucket_permission.py

app/schemas/user.py

app/tests/api/test_bucket_permissions.py

app/tests/api/test_buckets.py

app/tests/api/test_login.py

app/tests/api/test_s3_keys.py

app/tests/api/test_users.py