Missing identifier modifier in FHIRParameters.Modifier enum

[csandersdev]

Describe the bug
The conformance guide says that we support the Reference :identifier modifier, but it is not declared in the fhir-client module FHIRParameters.Modifier enum.

Environment
4.8.1

To Reproduce
Steps to reproduce the behavior:

1. View the code for the FHIRParameters.Modifier enum and note that identifier is missing.

Expected behavior
All supported modifiers are declared in the enum.

[csandersdev]

Something else to consider here is the value/utility of the TYPE member of the FHIRParameters.Modifier enum. If I'm writing client code and I want to filter on a specific type new FHIRParameters().searchParam( "subject", Modifier.TYPE, "23" ) isn't going to spit out what I want. It would be more useful to the client to have the ResourceTypes available as modifiers or specifiable in the searchParam method signature.

[csandersdev]

One more thought on FHIRParameters is that reference chaining is not well supported in the FHIRParameters class right now. If I wanted to do /Observation?subject:Patient.name=peter, I would have to construct that myself in the name of the query parameter vs. having the client construct it for me.

[csandersdev]

Looks like we are also missing the "of-type" modifier for token.

[csandersdev]

This covers most of what I mentioned above, but do we want to do anything in this PR around my third comment above regarding reference chaining? I'd be happy to split that into a separate issue if the team wants to handle that separately.

[tbieste]

This covers most of what I mentioned above, but do we want to do anything in this PR around my third comment above regarding reference chaining? I'd be happy to split that into a separate issue if the team wants to handle that separately.

Yeah, I prefer to keep things close to the original bug; to avoid feature creep in work items. If this satisfies the original bug, then opening a separate issue for the item in your third comment sounds good to me.

[lmsurpre]

Confirmed that the new prefixes were added to the enums and that the new :[type] modifier methods have unit test coverage.