Implement Endpoints 2.0 OperationContextParams

[jbelkins]

Describe the feature

Smithy 1.49.0 added support for string array endpoint parameters and operation context endpoint parameters.
https://github.com/smithy-lang/smithy/releases/tag/1.49.0

These features are generally described here:
https://smithy.io/2.0/additional-specs/rules-engine/parameters.html

String array-typed endpoint parameters are being implemented with the update to Smithy 1.49.0, but OperationContextParams will require greater work plus a bugfix:

• OperationContextParams defines a JMESPath (restricted to a limited JMES feature set) that we must code-generate into a Swift expression to get the needed params at runtime.
• There is also a bug in Smithy validation that prevents OperationContextParams from being defined on an operation without some extra trickery. Link to fix in main Smithy project: Add operationContextParams to RulesetParameterValidator smithy-lang/smithy#2295

Implement OperationContextParams once the validation bug has been resolved.

Use Case

To support all parameter field types on AWS endpoints.

Proposed Solution

No response

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

[jbelkins]

We use CRT to take our endpoint params & evaluate them against the endpoint rules.

Filed this ticket to allow us to set the Array<String> data type on the EndpointsRequestContext that is used to pass endpoint params into CRT:
awslabs/aws-crt-swift#266

[jbelkins]

Will investigate the plan for rolling this param out through services, so we can determine the appropriate priority for work.

[sichanyoo]

Note: check whether any change is needed in CRT.

[sichanyoo]

Tracked internally in SWIFT-1125