Release v4.210.0

Changed

• A file or inline command handler is now refused with its own error code PLAY0800 (command handler requires a constrained implementation attachment) instead of PLAY0268, with a required subject argument naming the command. PLAY0268 keeps meaning a construct is not representable in a supported executable model version yet, so tools can tell a permanent limitation from one that a later version admits. Tools that matched the handler refusal by PLAY0268 and its message text switch to PLAY0800. See the diagnostics reference. (#852)