Re-parse anonymous BPD parameter segments when loading a persisted instance

[Cosnavel]

Problem

persist() stores the BPD with the segments in the shape the then current library version could parse: business transactions it did not implement are kept as AnonymousSegment. A bank only resends the BPD when it bumps its own BPD version (HKVVB announces ours), so after a library upgrade those segments stay anonymous indefinitely.

Concrete case with #574: every connection that already had a persisted instance keeps reporting

The server does not support any DIKKUS versions implemented in this library

from GetCreditCardStatement, although the bank's BPD contains DIKKUS:45:2:3+1+1+0+90:N:J' — until the bank happens to change something in its BPD. The same applies to any segment added in the future (e.g. HIWPDS v6 from #480).

Change

• BPD::reparseAnonymousSegments() re-parses anonymous parameter segments through Parser::detectAndParseSegment(). AnonymousSegment serializes to the original wire format, so nothing is lost; segments the library still does not implement stay anonymous.
• FinTs::loadPersistedInstance() calls it after restoring the BPD.

Tests

Tests/Unit/Protocol/BPDReparseTest.php: an anonymous DIKKUS becomes DIKKUSv2 (speicherzeitraum 90) while an unknown segment stays anonymous, and the same through FinTs::new() with a persisted instance.

Note on authorship

Developed with AI assistance (Cursor) and reviewed by the submitting human; the vouching statement per #586 will be added by the author once the review is complete.

[Cosnavel]

@nemiah PR ist ready für's Review

[nemiah]

It probably won't break something and doesn't look too verbose for me. I'll merge it if your human takes responsibility

[Philipp91]

This looks good.

Just for consideration: An alternative solution would be to somehow figure out the library version (maybe it can know its own semver from the deployment somehow?) and persist it as part of the BPD or FinTs instance or so. Then upon re-init, if the persisted version doesn't match the current library version (in either direction), just discard the BPD, so we'll end up requesting it from the server again. This would additionally cover cases where the server sends different BPD when it receives a different request. That said, we haven't changed the request we send for BPD retrieval in many years, so probably this wouldn't matter.

[Cosnavel]

Thanks. I considered version-stamping, but the library can't reliably know its own version today (composer.json still says 4.1.0 on master, and many installs are dev-master#sha), and discarding the BPD costs an extra anonymous dialog per persisted instance after every deploy. The actual gap is narrower: segments are stored as wire text and re-parsed with the current classes on load already; only AnonymousSegment stays anonymous because __unserialize doesn't re-dispatch it — which is exactly what the re-parse closes, offline. If the BPD request itself ever changes incompatibly, the persist format version (2 in loadPersistedInstance()) seems like the right knob: bump it and drop the BPD for older blobs. Happy to do that as a follow-up if the request ever moves.