Enforce OperationDefinition affectsState

[prb112]

Is your feature request related to a problem? Please describe.
Enforce OperationDefinition affectsState per the Specification

OperationDefinition.affectsState
--
Element Id | OperationDefinition.affectsState
Definition | Whether the operation affects state. Side effects such as producing audit trail entries do not count as 'affecting  state'.
Cardinality | 0..1
Type | boolean
Summary | true
Comments | What http methods can be used for the  operation depends on the .affectsState value and whether the input  parameters are primitive or complex:   Servers SHALL support POST method for all operations.   Servers SHALL support GET method if all the parameters for the  operation are primitive or there are no parameters and the operation has  affectsState = false.

https://www.hl7.org/fhir/operationdefinition-definitions.html#OperationDefinition.affectsState

Describe the solution you'd like
The FHIROperation framework should read the affectsState per the Specification, and enforce the use of get/post

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Acceptance Criteria

1. GIVEN [a precondition]
   AND [another precondition]
   WHEN [test step]
   AND [test step]
   THEN [verification step]
   AND [verification step]

Additional context
Per Comment #2489 (comment)

[prb112]

Works great ...

With affectState off... flows right through.

With affectState on...
{"resourceType":"OperationOutcome","id":"c0-a8-56-25-c4336c9c-2d8c-4854-b9fa-99adefb54431","issue":[{"severity":"fatal","code":"not-supported","details":{"text":"HTTP method 'GET' is not supported for operation: 'testop'"},"expression":[""]}]}