feat: Add get-on-call-information action to backend plugin

[benjdlambert]

Description

OK, so this PR does a few things here.

First off, we're bumping to the latest 1.49 release. Whilst not strictly required, it's nice to be up to date 🎉 I also added

We're then adding a get-on-call-information action to the backend plugin, which takes integration keys from catalog entities and returns information including user details, schedule summaries, and escalation policy summaries.

I've deprecated the /oncall-users route, but happy to just break that if we think that's a better option, and replaced it with a /oncall endpoint instead which returns richer on-call data.

We've had this internally for some time but thinking it's better placed upstream 🙏

Affected plugin

• backstage-plugin
• backstage-plugin-backend
• backstage-plugin-scaffolder-actions
• backstage-plugin-entity-processor

Type of change

• New feature (non-breaking change which adds functionality)
• Fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• I have performed a self-review of this change
• Changes have been tested
• Changes have been tested in dark theme
• Changes are documented
• Changes generate no new warnings
• PR title follows conventional commit semantics

If this is a breaking change 👇

• I have documented the migration process
• I have implemented necessary warnings (if it can live side by side)

Acknowledgement

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