Support direct connections to ent from the rest api

[mdeicas]

Description of the PR

Adds configuration to allow endpoints from the REST API to connect directly to Ent. This will allow bypassing the GraphQl API to use database native functionality.

This option can be enabled with guacrest --db-direct-connection. Current endpoint implementations can be overridden to use this optimized implementation by adding methods to EntConnectedServer. If --db-direct-connection is specified but an endpoint does not have a corresponding EntConnectedServer implementation, then the default one will be used.

PR Checklist

• All commits have a Developer Certificate of Origin (DCO) -- they are generated using -s flag to git commit.
• All new changes are covered by tests
• If GraphQL schema is changed, make generate has been run
• If OpenAPI spec is changed, make generate has been run
• If collectsub protobuf has been changed, make proto has been run
• All CI checks are passing (tests and formatting)
• All dependent PRs have already been merged

[pxp928]

Very nice! @mdeicas

[mihaimaruseac]

Hmm, won't this create opportunities for the two backends to get out of sync? You'll now be able to write data that would not pass graphql ontology validations.

[mdeicas]

Hmm, won't this create opportunities for the two backends to get out of sync? You'll now be able to write data that would not pass graphql ontology validations.

Good point, that's true. This should only be for read access to the database, though. I think we can enforce this by adding a hook to the ent client to reject all writes, and also generally through code reviews.

[mihaimaruseac]

If we make it only read queries that works for me

[mdeicas]

@mrizzi @dejanb for visibility and any thoughts, I think you were interested in this!

[mihaimaruseac]

Thank you!