Adding endpoint for bulk retrieval of event definitions.

[dennisoelkers]

Description

Motivation and Context

This PR is adding an endpoint /events/definitions/byIds which allows bulk retrieval of event definitions by a given list of ids. In addition, it is fixing a couple of typing issues with the resource.

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.