Question regarding two PropertyDescriptors

[Dan S <ds...@gmail.com>]

Both processors PutAzureDataExplorer and PutDatabaseRecord each have
a PropertyDescriptor whose configuration does not seem to make sense. For
properties DATA_FORMAT (PutAzureDataExplorer)
and BINARY_STRING_FORMAT  (PutDatabaseRecord), each support expression
language expressions with flow file attributes and each have
allowable values (of which none the allowable values are an Expression
Language expression like in XMLReader for property RECORD_FORMAT).
How is it possible to have allowable values which only allow the user to
choose specific values and support Expression Language expressions using
flow file attributes that the user cannot enter?