L1-L2 Messaging
## Mike's notes
- L1<>L2 Messaging
- L2->L1 Messages
- Creating an L2->L1 Message
- Consuming an L2->L1 Message
- L1->L2 Messages
- Creating an L1->L2 Message
- Consuming an L1->L2 Message
- L2->L1 Messages
Ciara's notes
- There is LOADS in the current docs but idk if it is up-to-date or not (literally across guides, references and concepts rip)