[MEX-527] Memory Store cron jobs

[mad2sm0key]

Reasoning

• the API sufferes from performance degradation in high concurrent requests scenarios. This happens due to the high number of fields with resolver functions and the highly nested nature of certain models.
• the method propsed below, is meant to reduce load with the following strategy :

1. maintain certain complex models in a singleton (memory store)
2. hook into the graphQL lifecycle (bypass the regular resolve route) and return the data directly from the memory store

• this PR tackles point 1

Proposed Changes

• add cron jobs that initialize and maintain memory store data

How to test

• N/A