Remove init-method and use PostConstruct annotation

[RemiDesgrange]

Close #2504.

I also could not resist refactor this little lambda :-)

[fvanderbiest]

mfapp and sp do not build ?

[RemiDesgrange]

See #3000

[RemiDesgrange]

@fvanderbiest I'm going to wait for CI to work again, then I'll merge this.

[fvanderbiest]

mapfishapp builds not, "ImportError: No module named virtualenv"
We might miss something like

    - name: "Setting up Python 2.x"
      uses: actions/setup-python@v1
      with:
        python-version: '2.x'

    - name: "Installing jsbuild and virtualenv"
      run: |
        pip install jsbuild
        pip install virtualenv

in https://github.com/georchestra/georchestra/blob/master/.github/workflows/mapfishapp.yml

[landryb]

mapfishapp builds not, "ImportError: No module named virtualenv"

i had do do something similar in cadastrapp as it also uses jsbuild (from last millenium), maybe you want to reuse it.

[fvanderbiest]

i had do do something similar in cadastrapp as it also uses jsbuild (from last millenium), maybe you want to reuse it.

Comes from there ;-)

[RemiDesgrange]

I forgot to rebase on master. Now OK

[fvanderbiest]

Thanks !