ci: add on pull/push CI workflows

This commit adds the corresponding workflows for on pull and push actions, enabling
linting and unit testing.

.github/workflows/integrate.yaml

@@ -0,0 +1,32 @@
+# reusable workflow triggered by other actions
+name: CI
+
+jobs:
+
+  lint:
+    name: Lint Check
+    runs-on: ubuntu-20.04
+
+    steps:
+    - name: Check out code
+      uses: actions/checkout@v3
+
+    - name: Install dependencies
+      run: sudo apt-get install python3-pip tox
+
+    - name: Lint code
+      run: tox -e lint
+
+  unit:
+    name: Unit Test
+    runs-on: ubuntu-20.04
+
+    steps:
+    - name: Check out code
+      uses: actions/checkout@v3
+
+    - name: Install dependencies
+      run: sudo apt-get install python3-pip tox
+
+    - name: Run unit tests
+      run: tox -e unit

.github/workflows/on_pull_request.yaml

@@ -0,0 +1,14 @@
+name: On Pull Request
+
+# On pull_request, we:
+# * always publish to charmhub at latest/edge/branchname
+# * always run tests
+
+on:
+  pull_request:
+
+jobs:
+
+  tests:
+    name: Run Tests
+    uses: ./.github/workflows/integrate.yaml

.github/workflows/on_push.yaml

@@ -0,0 +1,20 @@
+name: On Push
+
+# On push to a "special" branch, we:
+# * always publish to charmhub at latest/edge/branchname
+# * always run tests
+# where a "special" branch is one of main/master or track/**, as
+# by convention these branches are the source for a corresponding
+# charmhub edge channel.
+
+on:
+  push:
+    branches:
+    - master
+    - main
+    - track/**
+
+jobs:
+  tests:
+    name: Run Tests
+    uses: ./.github/workflows/integrate.yaml