[Developer][Integration] Serialize schema- and field-level custom metadata in integration test JSON format

[asfimport]

I don't believe we are doing this at present. We should validate that each implementation properly handles the incoming metadata from other Arrow emitters

Reporter: Wes McKinney / @wesm
Assignee: Ben Kietzman / @bkietz

Related issues:

• [C++] Serialize Field metadata to IPC metadata (relates to)

PRs and other links:

• GitHub Pull Request #6556

_{Note: This issue was originally created as ARROW-2255. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
[~emkornfield@gmail.com] handling of Schema and Field custom_metadata is pretty inconsistent. To assert this is properly handled we would need to add it to the integration test JSON format

[asfimport]

Micah Kornfield / @emkornfield:
agreed.  I'll try to make this happen for 1.0.0.

[asfimport]

Wes McKinney / @wesm:
Looks like this is nearly done. I will review when I can

[asfimport]

Ben Kietzman / @bkietz:
Issue resolved by pull request 6556
#6556