Fix: elmogem compose needs to instanciate XML submit address

[Daetha]

ELMO-GEM docker-compose lacked a propper definition of email adress of GFZ Data Services

Changes

ELMO-GEM has now exactly 2 adresses for email submissions:

      # XML_SUBMIT_ADDRESS is for sending to data curators. In our case, GFZ Data Services
      # overrides it when a shared env file configures every variant.
      XML_SUBMIT_ADDRESS: "${XML_SUBMIT_ADDRESS}"
      # ICGEM registration mail
      ICGEM_SUBMIT_ADDRESS: ${ICGEM_SUBMIT_ADDRESS}

Notes for Reviewer

The propper testing will occur at the icgem-test server )

Checklist

Branching Strategy:

If this is a hotfix: The branch was created from main and will be merged into main.
If this is a feature or documentation change: The branch was created from dev and will be merged into dev.
If this is a feature or documentation branch, I have pulled the latest changes from main into my branch.

Code Quality

• My code follows the style guide.
• I have self-reviewed my code.
• I added comments for hard-to-understand code.
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Documentation

• If applicable, PHP code is documented using PHPDoc.
• If applicable, JavaScript code is documented using JSDoc.
• If needed, the ELMO Guide ('./doc/help.html') has been updated.
• If needed, the README has been updated.
• If needed, the API documentation ('./api/v2/docs') has been updated.
• If a new feature was added or a bug fixed, the changelog ('./doc/changelog.html') has been updated.

Testing

• If needed, Playwright tests have been updated or added.
• If needed, unit tests have been updated or added.
• If needed, jest tests have been updated or added.

Known Issues

[What lower priority problems remain?]