Is your feature request related to a problem? Please describe.
Related to #832 , medical_claim requires data_source, but this is not indicated in docs or tested for at run-time. Additionally, it has been decided to include data_source as part of the PK for all input layer tables to allow mapping of multiple sources within one connector. All tests and documentation needs to be updated to reflect this.

Describe the solution you'd like
data_source in the input layer models is indicated in docs as part of the PK.
data_source in the input layer models is tested as non-nullable and is included in the unique test for the model.
data_source in the core models is tested as non-nullable and is included in the unique test for the model.

Additional suggestion
Take data_source out of the id field construction in core eligibility, medical_claim, and pharmacy_claim since we are adding the field to the uniqueness tests.

Describe alternatives you've considered
An alternative in core models is to somehow include data_source in the construction of the id field, perhaps by concatenating it in.

Additional context
input layer eligibility, medical_claim, and pharmacy_claim already have data_source as part of the unique test, but do not have a nullability test.
core eligibility, medical_claim, and pharmacy_claim already include data_source as part of the id field by concatenating it into the resultant value.