Woodpecker CI: Add Docker stable releases

.woodpecker/docker-stable-combine.yaml

@@ -0,0 +1,27 @@
+when:
+  - event: push
+    branch: stable
+    path: [ "*.ex", "*.eex", "*.exs", "mix.lock", ".woodpecker/**" ]
+  - event: tag
+    branch: stable
+
+depends_on:
+  - docker-stable
+
+skip_clone: true
+
+steps:
+  docker-stable-combine:
+    image: git.fluffytail.org/phnt/wpc-docker-tagger:latest
+    settings:
+      registry: "git.fluffytail.org"
+      image: "pleroma-test/pleroma"
+      architectures: [amd64, arm64]
+      tags:
+        - latest
+        - stable
+        - ${CI_COMMIT_SHA}
+      username:
+        from_secret: pleroma-ci-user
+      password:
+        from_secret: pleroma-ci-password

.woodpecker/docker-stable.yaml

@@ -0,0 +1,52 @@
+when:
+  - event: push
+    branch: stable
+    path: [ "*.ex", "*.eex", "*.exs", "mix.lock", ".woodpecker/**" ]
+  - event: tag
+    branch: stable
+
+matrix:
+  platform:
+    - linux/amd64
+    - linux/arm64
+
+# This is needed for the when clauses below.
+# When the platform clause is fixed, this might not be needed anymore
+labels:
+  platform: ${platform}
+
+variables:
+  docker_variables: &docker_variables
+    repo: pleroma-test/pleroma
+    registry: git.fluffytail.org
+    username:
+      from_secret: pleroma-ci-user
+    password:
+      from_secret: pleroma-ci-password
+
+steps:
+  docker-stable-amd64:
+    image: woodpeckerci/plugin-kaniko:2.3.1
+    # when:
+    #   - platform: linux/amd64
+    # does not work even though it should according to docs
+    # https://github.com/woodpecker-ci/woodpecker/discussions/5367#discussioncomment-13901342
+    when:
+      - evaluate: platform == "linux/amd64"
+    settings:
+      <<: *docker_variables
+      tags:
+        - latest-amd64
+        - stable-amd64
+        - ${CI_COMMIT_SHA}-amd64
+
+  docker-stable-arm64:
+    image: woodpeckerci/plugin-kaniko:2.3.1
+    when:
+      - evaluate: platform == "linux/arm64"
+    settings:
+      <<: *docker_variables
+      tags:
+        - latest-arm64
+        - stable-arm64
+        - ${CI_COMMIT_SHA}-arm64