Add an optional name field for the Postgres adapter indexes configurations

[nazliander]

resolves dbt-labs/dbt-postgres#52

Problem

Currently Postgres Adapter does not accept a name field in the model indexes configurations. This might be unnecessary for some of the users. But for readability and maintenance, a meaningful index name can be helpful. As I understood from the previous threads this is mainly due to the need of unique names of indices within a transaction. I did not test or understood fully what is breaking. However, I wanted to follow the following threads and keep the original idea of uniqueness. So developed a solution bearing this in mind.

• DBT PostgreSQL not warning on indexes not getting created due to duplicate index name #1945 (comment)
• Support for postgres index creation? #804

Solution

Adding an optional name field in the Postgres Index Config. If the name is not provided the index name will be an MD5 hash of the index config contents as it was previously. If the name is provided then the Unix Time of the index creation will be concatenated to the name provided. This way we will have the benefit of both uniqueness and the semantics.

I also edited the relevant tests. This is my first time contribution attempt. Please let me know if there is something over or under developed. Happy to help.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX
• This PR includes type annotations for new and modified functions

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[dbeatty10]

Thanks for taking the time to open this PR @nazliander! Since opening, we've decoupled dbt Adapters from dbt Core, and this code now lives in a separate repo: dbt-postgres.

A consequence of the decoupling is that PR can't be merged anymore as is, so we're closing it. For more context see #9171.

The linked issue has already been transferred. Please don't hesitate to re-open your proposed code changes within this PR in the dbt-postgres repo.