Update add_rr_data_to_eicr to check if RR data is already present

[emmastephenson]

Action Requested

The RR extraction function add_rr_data_to_eicr needs to see if RR data has already been added to the eICR before it attempts to merge the fields.

Acceptance Criteria

If an eICR with RR data already combined into it and an RR are passed to the add_rr_data_to_eicr function, an exception is thrown. The exception should also be handled in the validation and FHIR conversion containers.

Additional Information

See this PR thread for context.