feat: add introspection support to query metadata from sqlq

[riyaz-ali]

This PR adds support for inspecting and querying meta-information from sqlq. Closes #22

[ramiroJCB]

is this completed ? otherwise lets change this to draft :)

[amenowanna]

@riyaz-ali Can you please document and expand on ENUM and Complex types like the ones you are introducing here in Notion. My concern on these types is that they will limit our compatibility. Postgraphile seems to support them. The docs for SQLC do not document their support (not saying they don't). We already have issues with porting our current schemas to other database providers that don't support things like UDF's and UUID and I would prefer not to add to the mix if we can. If we convert this to an ENUM table the portability increases IMO.

https://www.notion.so/mergestat/PostgreSQL-Schemas-5954fae036374c85a904d361149fc309

[riyaz-ali]

My reason behind having a custom type (and not simply using the underlying table definition) is that I don't want to expose the "internals" of the sqlq schema to the user. The only way I found with custom functions is to add a custom type and return that.

[patrickdevivo]

Just want to check in here on what the go-forward should be for this PR. Are we okay with ENUMs once we've documented them a bit internally as to why/where we'd choose to use them?

[amenowanna]

We are going to convert this to a draft PR as not all of the views we need have been identified and added. We will create a list of the views we need and start working to add them to this PR as we continue to work on them. This will not be a blocking draft as we will continue to work on the other issues. @riyaz-ali will also still need to document ENUMS in notion.

[codecov-commenter]

Welcome to Codecov 🎉

Once you merge this PR into your default branch, you're all set! Codecov will compare coverage reports and display results in all future pull requests.

Thanks for integrating Codecov - We've got you covered ☂️