Add config-script input

```
- uses: CargoSense/setup-elixir-project@v1
  with:
    config-script: |
      mix hex.repo add oban https://repo.oban.pro
        --fetch-public-key "${{ secrets.OBAN_KEY_FINGERPRINT }}"
        --auth-key "${{ secrets.OBAN_LICENSE_KEY }}"
```

Author: jgarber623-cargosense

.github/workflows/ci.yml

@@ -34,7 +34,10 @@ jobs:
         with:
           elixir-version: 1.15
           otp-version: 25
+          config-script: |
+            echo "hello, world" > hello.txt
       - name: Check Erlang and Elixir versions
         run: |
           elixir --version | grep 'Erlang/OTP 25'
           elixir --version | grep 'Elixir 1.15'
+          grep -q "hello, world" hello.txt

README.md

@@ -23,6 +23,9 @@
     # invalidate existing caches.
     # Default: "v1"
     cache-key: ""
+    # An optional Bash script to run before fetching and compiling dependencies.
+    # May be used to configure Mix or Rebar3.
+    config-script: ""
     # Compile application using `mix compile`.
     # Default: true
     build-app: true

action.yml

@@ -20,6 +20,10 @@ inputs:
       An arbitrary string added to the derived cache key names. Set or change to
       invalidate existing caches.
     default: "v1"
+  config-script:
+    description: >-
+      An optional Bash script to run before fetching and compiling dependencies.
+      May be used to configure Mix or Rebar3.
   build-app:
     description: Compile application using `mix compile`.
     default: true
@@ -116,6 +120,13 @@ runs:
       run: mix local.rebar --force
       shell: bash
 
+    - name: Run configuration script
+      if: inputs.config-script != ''
+      run: /bin/bash -c "${CONFIG_SCRIPT}"
+      shell: bash
+      env:
+        CONFIG_SCRIPT: ${{ inputs.config-script }}
+
     - name: Get out-of-date project dependencies
       run: mix deps.get
       shell: bash