[ci] Use OCIR for non-release PRs (#1226)

Changing the container registry from GHCR to OCIR will help with more
flexibe image retention policies and removes the restrictions on the
GitHub token when contributors submit PRs from forks. Release PRs remain
on GHCR, as before.

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## What this PR does


### Release note

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```release-note
[ci] Use OCIR for non-release PRs
```

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Chores**
* Updated workflow to use Oracle Cloud Infrastructure Registry (OCIR)
for Docker authentication instead of GitHub Container Registry.
* Improved environment variable handling to allow overriding the default
Docker registry setting.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

.github/workflows/pull-requests.yaml

@@ -1,5 +1,7 @@
 name: Pull Request
 
+env:
+  REGISTRY: ${{ secrets.OCIR_REPO }}
 on:
   pull_request:
     types: [opened, synchronize, reopened]
@@ -33,9 +35,9 @@ jobs:
       - name: Login to GitHub Container Registry
         uses: docker/login-action@v3
         with:
-          username: ${{ github.repository_owner }}
-          password: ${{ secrets.GITHUB_TOKEN }}
-          registry: ghcr.io
+          username: ${{ secrets.OCIR_USER}}
+          password: ${{ secrets.OCIR_TOKEN }}
+          registry: iad.ocir.io
         env:
           DOCKER_CONFIG: ${{ runner.temp }}/.docker
 

scripts/common-envs.mk

@@ -1,4 +1,4 @@
-REGISTRY := ghcr.io/cozystack/cozystack
+REGISTRY ?= ghcr.io/cozystack/cozystack
 PUSH := 1
 LOAD := 0
 COZYSTACK_VERSION = $(patsubst v%,%,$(shell git describe --tags))