consolidate demo plugins to common package

.github/workflows/testing_external_plugins.yaml

@@ -32,6 +32,11 @@ jobs:
             python-version: 3.9
 
     steps:
+    - name: Extract branch name
+      shell: bash
+      run: echo "##[set-output name=branch;]$(echo ${GITHUB_REF#refs/heads/})"
+      id: extract_branch
+
     - uses: actions/checkout@v2
 
     - name: Set up Python ${{ matrix.python-version }}
@@ -49,9 +54,9 @@ jobs:
       run: |
         pip install poetry
         poetry config --local virtualenvs.in-project true
-        poetry add git+https://github.com/MinchinWeb/jrnl-rot13-exporter.git
         poetry install --remove-untracked
-        poetry install 
+        poetry install
+        poetry run python -m pip install -e "git+${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}.git@{{ steps.extract_branch.outputs.branch }}#egg=jrnl-demo-plugins&subdirectory=tests/external_plugins_src"
 
     - name: Test with pytest
       if: success() || failure()