feat(github-enterprise): Add API-driven pipeline backend for GHE integration setup

[evanpurkhiser]

Implement get_pipeline_api_steps() on GitHubEnterpriseIntegrationProvider with three steps: installation config (URL, app credentials, keys), app install redirect (popup-based GitHub app installation with polling), and a late-bound OAuth step constructed from the config step's data. Includes serializers for each step and updates build_integration() to handle both legacy and API state paths.

Ref VDY-40

[linear-code]

VDY-40 GitHub Enterprise: API-driven integration setup

[getsantry]

This pull request has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you add the label WIP, I will leave it alone unless WIP is removed ... forever!

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"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀

[sentry]

Bug: The new GHEInstallationConfigSerializer uses URLField, which requires a URL scheme. This is a regression from the old form that accepted URLs without a scheme like github.example.com.
_{Severity: MEDIUM}

Suggested Fix

Modify the GHEInstallationConfigSerializer to handle URLs without a scheme, similar to the old form-based logic. This could involve using a custom field or overriding the validate_url method to prepend https:// if a scheme is missing before validation. This would restore the previous, more user-friendly behavior.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's
not valid.

Location: src/sentry/integrations/github_enterprise/integration.py#L565

Potential issue: The new API endpoint for configuring GitHub Enterprise integrations,
which uses `GHEInstallationConfigSerializer`, now requires the URL to include a scheme
(e.g., `https://`). This is because it uses `rest_framework.fields.URLField` for
validation. The previous form-based implementation was more lenient, using
`forms.CharField` and custom logic to handle URLs submitted without a scheme, such as
`github.example.com`. This change introduces a regression where users may encounter
unexpected validation errors for input that was previously accepted.

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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^{Reviewed by Cursor Bugbot for commit f5d0fc3. Configure here.}

[cursor]

API URL host normalization mismatch

Medium Severity

The GHEInstallationConfigApiStep incorrectly parses installation URLs when the hostname is in the path (e.g., example.com instead of https://example.com). This results in an empty host, leading to malformed OAuth URLs and bypassing the github.com feature gate.

 

^{Reviewed by Cursor Bugbot for commit f5d0fc3. Configure here.}