feat: Add resource for subscriptions

[nicarl]

This PR adds the new resource postgresql_publication for managing PostgreSQL publications.

Example:

resource "postgresql_subscription" "subscription" {
  name          = "subscription"
  conninfo      = "host=localhost port=5432 dbname=mydb user=postgres password=secret"
  publications  = ["publication"]
}

Key decisions:

• I decided to let the user pass conninfo as one string instead of adding fields for host, port, etc.
• There are additional options when setting up a subscription (https://www.postgresql.org/docs/current/sql-createsubscription.html), I did not add support for those yet to keep this as a small as possbile
• I could not find a reliable way to update individual parameters - destroy and recreate is therefore preferred
• For the testing one need to set the create_slot to false as the publisher is on the same database cluster. Otherwise the CREATE statement will hang. This is a known issue (https://www.postgresql.org/docs/current/sql-createsubscription.html)
• The tests get flaky when not waiting a few seconds after the test. This seems to be related to the replication slots. I choose a pragmatic solution here and added a cool down period of 5 seconds

fix: https://github.com/cyrilgdn/terraform-provider-postgresql/issues/238

[nicarl]

cc @chromko maybe you can have a look at this as you added the publication resource?

[nicarl]

Hey @cyrilgdn I ran the tests successfully on my local machine, I would be curious if they pass in the CI

[cyrilgdn]

@nicarl Thanks for you work on that :+1:

I would be curious if they pass in the CI

Just triggered them!

I'll try to review as soon as possible (hopefully this week-end)

[nicarl]

@nicarl Thanks for you work on that 👍

I would be curious if they pass in the CI

Just triggered them!

I'll try to review as soon as possible (hopefully this week-end)

Hey, did you have time to look at this?

[nicarl]

Hey @cyrilgdn the tests are passing, did you have any time to look at the PR?

[cyrilgdn]

Sorry for the absence of response, I was a bit off the project for a while due to lack of time.

I'll review it so we can include in the next release, could you just merge master to resolve the conflict (you can revert test.yml to the master version)

[cyrilgdn]

This has been released in v1.18.0

[nicarl]

Hey, sorry I did not find time earlier. Thank you for fixing the last details and your work for this provider! :bow: