Define Internal Message Schema

[Lan2u]

Currently, we use a loosely defined message structure internally based on JSON, now we have a bare-bones system and the API is being finalized it is worth defining the internal message schema used.

I'm planning to use https://json-schema.org/specification.html as per https://visualstudiomagazine.com/articles/2018/02/01/service-message-formats.aspx and then hopefully decouple message handling/format/verification from the actual functionality of the service. This should mean that new services like venue or equipment can be created quicker as a standard message handling module can be used by them all.

TODO as part of this

• Define the message schema formally using JsonSchema https://json-schema.org/specification.html
• Bring that schema into Typescript https://spin.atomicobject.com/2018/03/26/typescript-data-validation/
• Define a new module used by services for communication within the backend