[Feature] Support connection options

[sdebruyn]

Is this your first time submitting a feature request?

• I have read the expectations for open source contributors
• I have searched the existing issues, and I could not find an existing issue for this feature
• I am requesting a straightforward extension of existing dbt-postgres functionality, rather than a Big Idea better suited to a discussion

Describe the feature

Some Postgres connections require extra connection options. Add the configuration parameter options in the profile to support those use cases.
The parameter is documented in the Postgres docs.

Describe alternatives you've considered

No response

Who will this benefit?

dbt Cloud is using an outdated version of libpq which does not support SNI. Some providers rely on SNI and have built workarounds using connection options. Even if at some point dbt Cloud updates its libpq version (it should), extra connection options might still be useful.
An example is neon.tech, see this documentation page

Are you interested in contributing this feature?

Yes, if you confirm that you'd be willing to have this feature so that I don't put effort into a PR which you won't accept.

Anything else?

psycopg2 just accepts this like any other connection parameter. After adding the options as a string in the PostgresCredentials, this should be added in the kwargs right before this line.