warning.integrity.member_not_found should be an ERROR by default, with new flag to downgrade to warning

[jordanpadams]

Checked for duplicates

Yes - Related to #308 (which originally set this as a warning) and #1156 (accumulating bundles use case)

🐛 Describe the bug

When a collection inventory lists member products that cannot be found within the validating target, validate reports warning.integrity.member_not_found — a WARNING. This is incorrect default behavior.

A collection inventory explicitly declares its primary member products. Those products must be present within the target being validated. A missing member is a data integrity failure, not merely advisory. The warning severity was originally chosen in #308 to accommodate cross-bundle and accumulating bundle scenarios, but that accommodation should require an explicit user opt-in, not be the default.

🕵️ Expected behavior

By default, member_not_found should be reported as an ERROR.

A new CLI flag (e.g., --allow-unlisted-members) should be introduced to downgrade this condition back to a WARNING for users who are intentionally validating partial/incremental bundles where prior-release products are legitimately absent. This preserves the use cases documented in #308 and #1156 without masking real data errors for everyone else.

Proposed behavior summary:

• Default (no flag): member_not_found → ERROR
• With --allow-unlisted-members: member_not_found → WARNING (for accumulating/incremental bundle use cases)

📜 To Reproduce

1. Create or obtain a bundle where a collection inventory references one or more member products that are not present in the local target directory
2. Run: validate --rule pds4.bundle <path/to/bundle>
3. Observe that missing members are reported as WARNING [warning.integrity.member_not_found] instead of ERROR

Example output that should be an ERROR:

PASS: collection_context_inventory.xml (urn:isro:isda:ch2_cho:context::1.0)
    WARNING  [warning.integrity.member_not_found]   The member 'urn:isro:isda:ch2_cho:context:mission::1.0' could not be found in any product within the given target.
    WARNING  [warning.integrity.member_not_found]   The member 'urn:isro:isda:ch2_cho:context:instrument_host_spacecraft::1.0' could not be found in any product within the given target.

🖥 Environment Info

• Affects all current validate versions
• Reproduced with a PDS4 bundle using pds4.bundle validation rule

📚 Version of Software Used

All versions (behavior inherited from original #308 implementation)

🩺 Test Data / Additional context

Prior art and rationale for original warning level:

• As a user, I want to check that all Internal References are valid references to other PDS4 products within the current validating bundle #308: Original request explicitly asked for a warning because "products in one bundle routinely reference a product in another bundle." The cross-bundle and accumulating bundle use cases are real and valid, but they should require an explicit opt-in flag rather than being the silent default.
• As a user, I want referential integrity checks on accumulating bundles to use existing bundle #1156: Documents the accumulating bundle scenario — a partial/incremental delivery intentionally does not include products from prior releases. This use case should be supported via the proposed --allow-unlisted-members flag.

The fix requires:

1. Changing ProblemType.MEMBER_NOT_FOUND severity from WARNING to ERROR (or introducing a parallel ERROR type)
2. Adding a new CLI flag (e.g., --allow-unlisted-members) that restores WARNING behavior when set
3. Updating documentation and help text to describe the flag and its use case

🦄 Related requirements

• As a user, I want to check that all Internal References are valid references to other PDS4 products within the current validating bundle #308 (original implementation — warning was intentional but should now be opt-in)
• As a user, I want referential integrity checks on accumulating bundles to use existing bundle #1156 (accumulating bundles use case to be preserved via new flag)

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For Internal Dev Team To Complete

⚙️ Engineering Details

🎉 Integration & Test