Backwards compatibility policy

Related to https://github.com/apache/camel-quarkus/issues/2791 and similar issues a question arose when is it fine to commit backwards incompatible changes. A stable and explicit policy would help both maintainers to decide and end users to adjust their expectations.

* We should check whether Camel and Quarkus have some explicit polices
* It makes little sense to be more strict than they are.

Start by reviewing the related issue #2791 and checking whether Camel and Quarkus publish explicit backwards-compatibility policies. Compare those policies with Camel Quarkus needs and document a stable policy that explains when incompatible changes are acceptable and how end users should adjust their expectations.

Written by the indexing model from the issue text.