Add support for citext arrays

[eneagoe]

Currently if the tags column is of citext type, the generated SQL is invalid. Adding this extra configuration fixes the issue.

[skatkov]

Can you add some test as well, please? And a changelog entry.

[eneagoe]

Can you add some test as well, please? And a changelog entry.

Will do!

[eneagoe]

The new specs pass locally, but i'm afraid in order to enable the citext extension the PG user needs to be a super-user, so the specs fail on the CI server.

[skatkov]

@eneagoe I assume, CI could be fixed if you run application as superuser.

I ran through tests.yml configuration file:
https://github.com/tmiyamon/acts-as-taggable-array-on/blob/master/.github/workflows/tests.yml

It might be two things:

• Password for PG user is empty, but should be "postgresql".
• "Running a test" step might need an environment variable POSTGRES_USER.

But it's just my wild guess.

[eneagoe]

It looks a bit uglier now, but configuring the citext extension upfront for the test database should pass all the tests now - they do in my fork.

[skatkov]

CI is working.

But what would happen locally now, if I don't have citext enabled?

[eneagoe]

Good point - I've added a condition to enable the citext extension if it's not already enabled on the test database.

[skatkov]

@eneagoe thanks for contribution -- seems to be working locally for me too.

I'll merge this and release a new gem.

[eneagoe]

@skatkov Thank you for your time and help!