Don't leak overwrite kwarg into plugin validated_data

[daviddavis]

Problem

The overwrite field added in #7550 (commit f6dc7b9) on NoArtifactContentSerializer was declared with default=True. DRF auto-injects any field with a default=... into validated_data even when the caller does not supply it, so plugins that splat **serializer.validated_data into a content model constructor were broken by the unexpected overwrite=True kwarg.

For example, in pulp_deb's sync stage (pulp_deb/app/tasks/synchronizing.py:1057):

serializer = serializer_class.from822(data=package_paragraph)
serializer.is_valid(raise_exception=True)
package_content_unit = package_class(
    relative_path=package_relpath,
    sha256=package_sha256,
    **serializer.validated_data,   # <-- now contains overwrite=True
)

The Django Package model has no overwrite field, so:

TypeError: Package() got unexpected keyword arguments: 'overwrite'

This caused 10 functional test_sync tests in pulp_deb to fail.

The other inherited control fields on NoArtifactContentSerializer (repository, pulp_labels) don't trigger the same issue because none of them declare a default=, so DRF only puts them into validated_data when explicitly supplied. overwrite was the only one that leaked unconditionally.

Fix

Remove the default=True from the field declaration. The existing validated_data.pop("overwrite", True) in NoArtifactContentSerializer.create() already encodes the "absent ⇒ True" semantics, so there is no behavior change for REST API callers:

Caller behavior	Before	After
Omits overwrite	validated_data["overwrite"] = True, pop returns True → silent overwrite	Field absent from validated_data, pop("overwrite", True) returns True → silent overwrite
Sends overwrite: false	Field validates → False in validated_data → check runs	Same
Sends overwrite: true	Field validates → True in validated_data → silent overwrite	Same

Verification

• All 7 existing tests in pulp_file/tests/functional/api/test_overwrite_content.py still pass.
• The 10 pulp_deb test_sync failures are resolved by this change alone.

AI attribution

AI-Generated: github-copilot

[patchback]

Backport to 3.111: 💚 backport PR created

✅ Backport PR branch: patchback/backports/3.111/e2c3f4dbf4620feb16b27c5c11b3a9ae920d067e/pr-7717

Backported as #7718

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