Merge pull request #72 from sdresselmann/task/#63_refactor_firestore_service

#61 - task(firestore service): remove commented out code

#61 - task(firestore service): rename firestore service methods

#61 - task(firestore service): add service interface for firestore API

#61 - task(firestore service): add converters for firestore data

#61 - task(firestore service): remove raw firebase data type

Merge pull request #71 from sdresselmann/task/update_dependencies

#61 - task(pipeline): revert adding github secret key

#61 - task(pipeline): add github secret keys to test run

#61 - task(pipeline): update flutter version

#61 - task(.env): replace env calls with dart define

#61 - task(.env): delete .env from vcs

#61 - task(.env): delete .env from vcs

Rename CONTRIBUTE.md to CONTRIBUTING.md

Rename contribute.md to CONTRIBUTE.md