Update Epics API for Grape 1.7 compatibility

What does this MR do and why?

Contributes to #395809 (closed)

The previous version had a bug and was reverted: !122042 (merged).

Problem

There is a change to parameter renaming functionality in Grape >= 1.6.0. https://github.com/ruby-grape/grape/blob/master/UPGRADING.md#upgrading-to--160

We need to update parameters for compatibility reasons.

Solution

Don't use as for parameters renaming. Instead define two separate params and apply the transformation.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.