Support granular API tokens in Jira integration

[michelle-luana]

Prerequisites

• I have searched open and closed issues to make sure it isn't already requested
• My team has started working on this issue
• I have written a descriptive issue title

Summary

The current Jira integration only supports the legacy authentication approach, which requires a dedicated Jira user with broad permissions and uses the instance-direct URL (https://.atlassian.net). We need to add support for Jira's newer granular API tokens, which use a different base endpoint.

Background

Jira's granular (OAuth 2.0) API tokens route requests through:
https://api.atlassian.com/ex/jira/<cloudId>
rather than the instance-direct URL the integration currently uses. These two authentication approaches are not interchangeable — the endpoint itself is different, so supporting the new token type requires handling both URL patterns.

Problem

Customers who want to use granular API tokens (which allow scoped, least-privilege access) are currently blocked. To use the integration at all, they're forced to:

Create a dedicated "dummy" Jira user
Grant it broad/full access to work around the limitations of the legacy token approach

Requested change

Update the Jira integration to support granular API tokens by:

Accepting a Cloud ID (or deriving it automatically) when a user configures the integration
Routing API calls through https://api.atlassian.com/ex/jira/ when a granular token is provided
Ideally, allowing users to choose between legacy and granular token modes in the integration config UI