feat(server/core): generalize caching mechanism, and update getServerInfoFactory to rely on getServerConfig dependency

[iainsproat]

Description & motivation

Following the pattern set by knex, we instantiate a client (in this case the cache directly) in a central location which can be accessed by all callers.

Separates the caching retrieval and setting to a general, and generic, handler.

We provide a handler around the knex query to get the server config, allowing it to be used in the caching handler.

We update all references of getServerInfo to use the new signature. For now, we have these directly call the db without caching (except in the resolver which is already cached).

Changes:

• health check of postgres now retrieves server config, not server info. health check should never be cached (bustCache is always set to true, even though it uses a method without caching).
• cache value in memory with short TTL (configurable); this is created in the module to be used by all calls to server info where required.
• server config is a dependency of server info, and has to be passed in by all callers
• for now, the majority of calls do not go via the cache. Instead using getServerConfigFactory to call the database directly

To-do before merge:

Screenshots:

Validation of changes:

Checklist:

• My pull request follows the guidelines in the Contributing guide?
• My pull request does not duplicate any other open Pull Requests for the same update/change?
• My commits are related to the pull request and do not amend unrelated code or documentation.
• My code follows a similar style to existing code.
• I have added appropriate tests.
• I have updated or added relevant documentation.

References

[linear]

WEB-2432 Cache server_config queries

[gjedlicska]

closing in favor of a leaner approach in #3808