Release v4.207.0

Added

• The protected command read diagnostics PLAY0781–PLAY0785 carry typed arguments, so tools can read why a read could not be protected instead of parsing message text. They identify the command and the read, and PLAY0781 adds the read model and a reason keyword (reducer, join, no-removal, key-type, …). Every refused read gets its own diagnostic, and messages are unchanged. See diagnostics. (#851)