Proposal: Adding the managingOrganization property to the Patient Model

[FredMCK125]

This proposal is quite simple and aims at adding the missing managingOrganization property to the patient model.

It seems to be working nicely on my local branch using the existing fhir_utils methods.

Adding this line to the data-contract.json
"managing_organization": "managingOrganization"
Generates the following output from the table column managing_organization
"managingOrganization": { "display": "LIO-001", "reference": "Organization/LIO-001" },

I would be happy to publish my branch for a PR if this modification is deemed useful.

[evbaron]

I believe this is part of R4 and would be a good contribution.