Review caching implementation

Problem/Motivation

Caching in this module should be reviewed and checked to ensure it works as expected. Currently our theme type doesn't have a #cache value and we should also check the block caching.

Without any caching information added, this will be cached forever and presumably without cache dependencies.

Might be correct or not.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes