Maintain latest changes in main branch

[evegufy]

Description

Maintain latest changes in main branch aka in the default branch. For the following repositories the latest changes are currently maintained in the dev branch:

• https://github.com/eclipse-tractusx/portal
• https://github.com/eclipse-tractusx/portal-frontend
• https://github.com/eclipse-tractusx/portal-frontend-registration
• https://github.com/eclipse-tractusx/portal-backend
• https://github.com/eclipse-tractusx/policy-hub
• https://github.com/eclipse-tractusx/ssi-credential-issuer
• https://github.com/eclipse-tractusx/ssi-authority-schema-registry

Acceptance Criteria

• [x] Adjust workflows - especially autodeployment (to dev environment) for Portal - to work with main branch instead of dev
• [x] Adjust branch protection rule
• [x] Coordinate change in development process within team and update documentation

Benefits

• Lower barrier of entry for open community
• Reduce risk of redundant work: if the latest changes remain in the dev branch it's less transparent that a change (feat or bug) might have already been implemented

[evegufy]

Enabled for https://github.com/eclipse-tractusx/ssi-authority-schema-registry in as part of https://github.com/eclipse-tractusx/ssi-authority-schema-registry/pull/16 and https://github.com/eclipse-tractusx/ssi-authority-schema-registry/pull/14 Informational, updated dev flow