improve branch concept to improve CI/CD

[FrankHossfeld]

Currently the mustangproject uses only a master-branch. Improving the branch concept will help to improve the stability of the library and automate the deployment.

dev-branch

this branch will contain the latest commits and so the current development state. (might be useful to change the version to HEAD-SNAPSHOT). Development will be done be creating a new branch from dev. Once done, a PR is created and - when approved - be merged into dev. This will trigger the build action. (see #655). In case all steps of the action runs successfully, a new HEAD-SNAPSHOT is deployed to Maven Central. This will prevent people from building the library locally and offer the possibility to test new features earlier.

main-branch

This branch contains the releases.

doing a release

To create a new release create a new branch from dev and call it for example release/x.x.x. Inside this branch change the version number to the new version of the release and merge the branch into main. Merging the branch will trigger a GitHub action, which builds, tests owasps and deploy the libraries.

To avoid merging conflicts with the next release, the main branch needs to be merged into the dev branch.