Absent validation for composite SearchParameter components types

[volodymyr-korzh]

Composite SearchParameter’s can only be composed out of the following 4 types of basic SearchParameter definitions: STRING, TOKEN, DATE, QUANTITY
But now it is possible to create composite SearchParameter with any type.

Steps To Reproduce

1. Create a SearchParameter based on a "type": "token".
2. Create another SearchParameter based on a "type": "reference".
3. Create a Composite SearchParameter which uses both of the above in its "component" definition.
4. If you try and use this Composite SearchParameter in a GET Request, you will get the following ERROR Response:

{
    "resourceType": "OperationOutcome",
    "issue": [
        {
            "severity": "error",
            "code": "processing",
            "diagnostics": "HAPI-1204: Don't know how to handle composite parameter with type of REFERENCE"
        }
    ]
}

Requests Example:

1. PUT {Server_URL}/SearchParameter/observation-code

{
	"resourceType": "SearchParameter",
	"id": "observation-code",
	"url": "http://hl7.org/fhir/SearchParameter/Observation-code",
	"status": "active",
	"code": "observation-code",
	"base": [
		"Observation"
	],
	"type": "token",
	"expression": "Observation.code"
}

2. PUT {Server_URL}/SearchParameter/observation-patient

{
	"resourceType": "SearchParameter",
	"id": "observation-patient",
	"url": "http://hl7.org/fhir/SearchParameter/Observation-patient",
	"status": "active",
	"description": "The subject that the observation is about (if patient)",
	"code": "observation-patient",
	"base": [
		"Observation"
	],
	"type": "reference",
	"expression": "Observation.subject.where(resolve() is Patient)",
	"target": [
		"Patient"
	]
}

3. POST {Server_URL}/SearchParameter

{
	"resourceType": "SearchParameter",
	"extension": [
		{
			"url": "http://hapifhir.io/fhir/StructureDefinition/sp-unique",
			"valueBoolean": false
		}
	],
	"status": "active",
	"code": "patient-code",
	"base": [
		"Observation",
		"Patient"
	],
	"type": "composite",
	"expression": "Observation",
	"component": [
		{
			"definition": "SearchParameter/observation-code",
			"expression": "Observation"
		},
		{
			"definition": "SearchParameter/observation-patient",
			"expression": "Observation"
		}
	]
}

4. GET {Server_URL}//Observation?patient-code:code$loinc|8302-2,value$1409

Actual result
Composite search parameter with "reference" component created successfully, but composite search query fails in runtime.
Expected behavior
Creation of Composite search parameter with "reference" component should be prohibited.