Remove Geo system hooks for 10.0

In 9.4, we deprecated system hooks for Geo.

In 10.0, we should kill them for good. Here's what we need to do to remove them:

• Remove Geo API receive hook handling
• Change the GeoNode model's repair functionality (update_dependents_attributes)
• Create a migration to remove the system hook
• Add some sort of diagnostic/warning that SSH key lookups via DB is the only supported way

Remaining event log work:

• We need to finish supporting project creations via event log: !2807 (merged)
• We need to finish supporting project renames via event log: !2615 (merged)

Other work:

• Minimize repository/file download update times: it could take ~10 minutes for an event to be seen by cursor and then updated by the worker: #3230 (closed)
• [?] Make Geo cursor more reliable (?)
• Refactor Gitlab::Geo::LogCursor.handle_repository_delete

@to1ne This might be a good starter task.

@dbalexandre @brodock Did I miss anything?

changed milestone to %10.0

changed the description

mentioned in issue #2174 (closed)

mentioned in issue #846

changed the description

assigned to @to1ne

changed the description

mentioned in merge request !2644 (merged)

We need to finish supporting project creations via event log

Geo::RepositorySyncWorker handles project creation for new projects, but I think that is worth to support this event via event log to at least make sure the repository exists on the secondary.

mentioned in issue omnibus-gitlab#1106

marked the checklist item Remove Geo API receive hook handling as completed

marked the checklist item Change the GeoNode model's repair functionality (update_dependents_attributes) as completed

marked the checklist item Create a migration to remove the system hook as completed

marked the checklist item Add some sort of diagnostic/warning that SSH key lookups via DB is the only supported way as completed

changed the description

!2644 (merged) is merged, and other items are being covered in separate issues/MRs, so I'm closing this one.

closed