Invalidate last_update_date when source changes

[oliverchang]

Currently, if we change e.g. a bucket or REST endpoint in a SourceRepository and reimport, we may have the following race condition with these checks:

osv.dev/docker/importer/importer.py

Line 465 in 6b36cfb

if not ignore_last_import_time and \

osv.dev/docker/importer/importer.py

Line 671 in 6b36cfb

if not ignore_last_import_time and (last_modified

This checks whether the candidate record was updated since the last SourceRepository update as an optimisation.

However, if the bucket/REST URL changes, this is irrelevant, and could lead to missed imports because the new bucket/REST URL could've been populated before the last SourceRepository import with the old source.

[github-actions]

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[andrewpollock]

To confirm my understanding of the problem:

for a given source "foo", initially configured to use GCS bucket or REST URL "bar", the potential race condition is when "foo" is reconfigured to use "baz" instead?