Don't rely on endpoint params region

[dagnir]

Motivation and Context

When generating the for the endpoint interceptor, don't assume that the
endpoint params contains a 'region' member; endpoint rulesets are not
required to have this parameter; in situations where the endpoint params
does not have this member, compilation fails.

For backwards compatibility, give the region endpoint params preference
if it exists; otherwise use the region from the execution attributes.

Modifications

Testing

• new codegen tests

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• I have read the CONTRIBUTING document
• Local run of mvn install succeeds
• My code follows the code style of this project
• My change requires a change to the Javadoc documentation
• I have updated the Javadoc documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed
• I have added a changelog entry. Adding a new entry must be accomplished by running the scripts/new-change script and following the instructions. Commit the new file created by the script in .changes/next-release with your changes.
• My change is to implement 1.11 parity feature and I have updated LaunchChangelog

License

• I confirm that this pull request can be released under the Apache 2 license

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[dagnir]

Realized there's a forwards compatibility issue if a service adds a region endpoint param in the future that does not use the AWS:Region builtin. Removed approval to prevent merging and will update with a more suitable fix.

Reevaluating fix.

[dagnir]

Closing this PR for now. Will revive once we settle on the solution as a team.

[github-actions]

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