Add a programmer friendly code to Persistent Task Assignments (#53711) #110013
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When a task can not be assigned, the ptask framework is able to message back a reason in form of a string. This feature also started to be used for successful assignments, for example in the task that ads a health node.
Callers might need to interpret an assignment failure to e.g. return a HTTP status code. A string is hard to interpret and therefore not suitable.
Therefore, the Assignment can now take a programmer friendly code. It is still possible to provide a freetext String, as some context dependent information (e.g. nodeId) can not be stored in an Enum. Because some tasks provided multiple reasons for being unable to assign (all concatenated in a string), it is possible to provide multiple codes.
This commit also adapted the serialization and deserialization methods for backwards compatibility.
Closes #53711