strings not handled correctly

[rerpha]

Strings are not handled correctly by the CA update handler. Messages like this are shown in the logs:

ERROR - Got error when handling CA update for response EventAddResponse(data=[b'Ramping'], data_type=<ChannelType.TIME_STRING: 14>, data_count=1, status=CAStatusCode(name='ECA_NORMAL', code=0, code_with_severity=1, severity=<CASeverity.SUCCESS: 1>, success=1, defunct=False, description='Normal successful completion'), subscriptionid=125, metadata=DBR_TIME_STRING(status=<AlarmStatus.NO_ALARM: 0>, severity=<AlarmSeverity.NO_ALARM: 0>, timestamp=1741362795.672489)). Message was: f144 flatbuffer does not support values of type <U7.

This should be reasonably easy to reproduce, you just need a block pointing at at string value.