[Feature]: Shared caching functionality

### Description

We're using caching for external service calls (GitHub, Jira) in some places. Build a consolidated pattern that can be used across 3rd party API calls

### Use case

Speed up loading for 3rd party data like issues, stories, ...

### Area

Backend (Lambda)

### Additional context

_No response_

Start by locating the existing caching used for GitHub and Jira calls in the backend Lambda. Compare those call sites and define the scope of a shared pattern for third-party API calls; done means it can support loading data such as issues and stories more quickly.

Written by the indexing model from the issue text.