feat(ci): better rust CI

.github/workflows/api.yml

@@ -1,41 +0,0 @@
-# todo: use https://github.com/jpribyl/action-docker-layer-caching
-# todo: make this generic for all Rust images in this repo
-# todo: don't use docker/build-push-action
-# todo: run builds on pull request
-
-name: Build and push API Docker image
-on:
-  push:
-    branches:
-      - main
-      - 'rust-api'
-    paths:
-    - 'lib/pklib/**'
-    - 'services/api/**'
-
-jobs:
-  deploy:
-    runs-on: ubuntu-latest
-    permissions:
-      packages: write
-    if: github.repository == 'PluralKit/PluralKit'
-    steps:
-      - uses: docker/login-action@v1
-        with:
-          registry: ghcr.io
-          username: ${{ github.actor }}
-          password: ${{ secrets.CR_PAT }}
-      - uses: actions/checkout@v2
-      - run: echo "BRANCH_NAME=${GITHUB_REF#refs/heads/}" >> $GITHUB_ENV
-      - uses: docker/build-push-action@v2
-        with:
-          # https://github.com/docker/build-push-action/issues/378
-          context: .
-          file: Dockerfile.rust
-          push: true
-          tags: |
-            ghcr.io/pluralkit/api:${{ env.BRANCH_NAME }}
-            ghcr.io/pluralkit/api:${{ github.sha }}
-            ghcr.io/pluralkit/api:latest
-          cache-from: type=registry,ref=ghcr.io/pluralkit/pluralkit:${{ env.BRANCH_NAME }}
-          cache-to: type=inline