Feature: max-connections parameter

[bkoelman]

When running a large number of tests, it is often desirable to increase the max_connections parameter of the server. For example:

    - name: Setup PostgreSQL
      uses: ikalnytskyi/action-setup-postgres@v8
      with:
        username: postgres
        password: postgres

    - name: Configure PostgreSQL
      shell: bash
      run: |
        PGDATA="$RUNNER_TEMP/pgdata"
        echo "max_connections = 500" >> "$PGDATA/postgresql.conf"
        pg_ctl restart --pgdata="$PGDATA" --wait

It would be nice if this action could provide a parameter for that, so I can just use:

    - name: Setup PostgreSQL
      uses: ikalnytskyi/action-setup-postgres@v8
      with:
        username: postgres
        password: postgres
        max_connections: 500