Add stabilization phase description to developers guide

docs/manual/developer/10_stabilization_phase.md

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+# Stabilization Phase
+
+## Definition
+A period of time before release, when the project is extensively tested and the only accepted contributions are fixes to issues discovered during stabilization testing.
+New content, features, tests, or improvements are not accepted.
+Fixes for known issues that haven't been discovered during the stabilization process are also not accepted.
+
+To not interfere with project liveliness, the stabilization happens in a separate branch with *stabilization* prefix, e.g. stabilization-v0.1.70.
+Master/main branch contributions are not affected.
+
+During this period, project is tested, contributors are informed about upcoming release, everything is prepared for release (release notes, contributors list, milestones), and issue fixes are verified.
+
+## Duration
+Current duration is set to **2 weeks**.
+This duration is approximate.
+Complications such as newly discovered major issues during this period might slightly prolong it.
+
+The duration is tied to release cadence.
+The more time between release, the more time for stabilization is needed.
+Thus, the current 2 weeks stabilization is for release every 2 months.
+However, stabilization period does not affect release cadence.
+Next release date will be the same as there would not be any prolongation.
+
+## Exit Criteria
+Criteria that must be met for stabilization conclusion (in stabilization branch):
+- No major issues (build fails, remediation breaks system, built artifacts are invalid) in project,
+- All newly discovered issues are reported and fixed or planned for future release based on maintainers' discretion,
+- Issue fixes are either verified or re-opened and planned for future release,
+- Preparations for release (release notes, contributors list, milestones) are finished.
+
+With that, the stabilization phase can be concluded.
+If it happens before the planned release date, the decision is upon release assignee to either release earlier or wait until the date.