Add automatic Fastly cache purging to MFE pipelines

[Copilot]

MFE deployments to S3 were not invalidating Fastly CDN cache, causing stale content to be served after builds.

Changes

• pipeline.py: Added purge_fastly_cache and fastly_service_prefix fields to OpenEdxVars model
• pipeline.py: Conditional purge task appended to mfe_build_plan after S3 sync, calls Fastly /purge_all API
• values.py: Enabled purging for all deployments with environment-specific prefixes:
  • mitx: mitx_
  • mitx-staging: mitx_staging_
  • mitxonline: learn_
  • xpro: xpro_

Implementation

Follows existing pattern from mitlearn_nextjs pipeline. Service IDs resolved from Concourse secrets via ((fastly.{prefix}service_id_{env})) (e.g., ((fastly.mitx_service_id_ci))).

if open_edx.purge_fastly_cache and open_edx.fastly_service_prefix:
    fastly_service_id_key = (
        f"{open_edx.fastly_service_prefix}service_id_"
        f"{open_edx.environment_stage.lower()}"
    )
    mfe_build_plan.append(TaskStep(...))  # curl POST to Fastly API

Applies to all environment stages (CI, QA, Production) across all four deployments.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• astral.sh
  • Triggering command: /usr/bin/curl curl -LsSf REDACTED (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>automatic fastly purge to MFE builds</issue_title>
<issue_description>### Description/Context
Add automatic fastly cache purging to the MFE build + deployment jobs
https://cicd.odl.mit.edu/teams/main/pipelines/mfe-meta-pipeline
https://cicd.odl.mit.edu/teams/mitx-staging/pipelines/mitx-staging-master-mfe-pipeline
https://cicd.odl.mit.edu/teams/mitxonline/pipelines/mitxonline-master-mfe-pipeline
https://cicd.odl.mit.edu/teams/xpro/pipelines/xpro-ulmo-mfe-pipeline
etc

Plan/Design

</issue_description>

<agent_instructions>Refer to the mitlearn_nextjs pipeline for an example of an automatic Fastly purge in the pipeline. </agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes automatic fastly purge to MFE builds #4125

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