feat(experimentalIdentityAndAuth): Add generic @httpApiKeyAuth support

[syall]

Issue #, if available:

N/A.

Description of changes:

NOTE: All of these are under the experimentalIdentityAndAuth feature flag

NOTE: Dependent on #881

• Adding config properties apiKey:

  /**
   * The API key to use when making requests.
   */
  apiKey?: ApiKeyIdentity | ApiKeyIdentityProvider;

• @smithy/experimental-identity-and-auth package: add the ApiKeyIdentity interface and ApiKeyIdentityProvider type, HttpApiKeyAuthLocation enum, and default HttpApiKeyAuthSigner implementation.
• Add back operations that support @httpApiKeyAuth in the generic client test

Testing:

• @httpApiKeyAuth client codegen diff given the following model changes: https://gist.github.com/syall/a595c7738c380176a528ff29016f1c2c#file-httpapikeyauth-trait-client-diff
  • The existing integration generated middleware and tests in the client package, which is why there is such a large removal in the diff.

   @fakeProtocol
   // feat(experimentalIdentityAndAuth): uncomment operations as individual
   //   auth scheme support is implemented
  -// @httpApiKeyAuth(name: "X-Api-Key", in: "header")
  +@httpApiKeyAuth(name: "X-Api-Key", in: "header")
   // @httpBearerAuth
   // @sigv4(name: "weather")
   // @auth([sigv4])
  @@ -26,12 +26,12 @@ service Weather {
           // feat(experimentalIdentityAndAuth): uncomment operations as individual
           //   auth scheme support is implemented
           // experimentalIdentityAndAuth
  -        // OnlyHttpApiKeyAuth
  +        OnlyHttpApiKeyAuth
           // OnlyHttpBearerAuth
           // OnlyHttpApiKeyAndBearerAuth
           // OnlyHttpApiKeyAndBearerAuthReversed
  -        // OnlyHttpApiKeyAuthOptional
  -        // SameAsService
  +        OnlyHttpApiKeyAuthOptional
  +        SameAsService
       ]
   }

• No codegen diff for aws-sdk-js-v3

If one or more of the packages in the /packages directory has been modified, be sure yarn changeset add has been run and its output has
been committed and included in this pull request. See CONTRIBUTING.md.

---

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.