perf: index garbage collector

[Galeaf11]

Problem

The proposed solution for managing the leveldb creates a few indices that are used to store mappings. Over time, these indices will grow and potentially reduce the performance of lpms-server.

Solution

Establish a garbage collection routine whereby indices can automatically be trimmed from the database when not required. Care must be given not to delete information that would be required for audit purposes.

[mfw78]

@lucarioams Can you please provide some input to this (not a high priority) as to how long lookup data / booking data should be retained, or do we just make this another configuration option, with a sane default value?

[xdaluca]

I think we should have a sane default here, e.g. 90-days. After that it gets deleted, they can chose to export it first and store it if they want.