Using Activity isolation as a security boundary

What this post added

This post details a specific architectural pattern for enhancing security by consolidating PII scanning, classification, and storage within a single Temporal Activity. It addresses the trade-offs of deviating from the 'single-purpose Activity' guideline for compliance reasons. The post also elaborates on implementing a swappable storage layer using a `DataStore` protocol and demonstrates how heartbeating can be used to detect stuck Workers in long-running streaming Activities, enabling resumable processing.