{source-materialize}-postgres: support JSONB

[mdibaiee]

Description:

• Use a custom contentMediaType: "application/vnd.postgresql.jsonb+json" annotation in JSONSchema to mark an object as originating from a postgresql JSONB column type
• In materializations, use JSONB for creating such a column
• Add automatic column migrations from JSON to JSONB and vice versa

I have identified customers that would be affected by this and I am coordinating with our support team to make sure we can transition them to this new change without breaking their pipelines down the line.

Workflow steps:

(How does one use this feature, and how has it changed)

Documentation links affected:

(list any documentation links that you created, or existing ones that you've identified as needing updates, along with a brief description)

Notes for reviewers:

(anything that might help someone review this PR)

[danielnelson]

Both json and jsonb are encoded in the collection in the same way, so it doesn't seem like the media type is describing anything about the actual format of the data. It also see that contentMediaType is described only for strings.

I feel like we potentially could need to invent media types for every possible source type? I'm also imagining things like a request for mirroring aspects such as string collation. We do already have the information in the description and while it's not super machine readable we could try parsing.

Or perhaps we would be better served with a new custom annotation for source type?

[mdibaiee]

@danielnelson that was a great point I had overlooked. I had a chat with data plane folks and they were happy to have contentMediaType for all types, so I'm working on a PR for that estuary/flow#2945