Enable support for Maintainer token role for integration

[subbuvenk-atlas]

Description

Adds support for the new Maintainer token role throughout the app. Covers all cases of:

• Connecting new group + webhook
• Fetching existing group and linked projects details for state
• Data provider for import flow

Checklist

Please ensure that each of these items has been addressed:

• I have tested these changes in my local environment
• I have added/modified tests as applicable to cover these changes
• (Atlassian contributors only) I have removed any Atlassian-internal changes including internal modules, references to internal tickets, and internal wiki links

Testing

Manually walked through the various flows for both Owner and Maintainer tokens ensuring existing pathways remain unaffected.