Spreadsheet of key fields (e.g from MCR and others), and include this in the docs

[nickevansuk]

[nishaldesai]

@nickevansuk here's what I've got so far:
spreadsheet of key fields, defining Essential (in use across many activity finders, often is a prerequisite before use of a feed), Useful (should be included otherwise activities less searchable) and Nice to Have (decent benefit to the end user or data consumer). There's also "no precedence" for where I've not seen any specific evidence of a data field having high usage / focus of discussions:
https://docs.google.com/spreadsheets/d/1Z8edUJwj-hdrgmrGjB1h8v2MoB_FUf5tbc6TDvcXWak/edit#gid=0

Yellow cells are where I wasn't sure exactly or where I couldn't find the content in the spec or docs.

I've been through previous customers and the MCR data fields requirement sheet, as well as looking at what data fields MCR actually ended up using.

I've ignored anything outside of Events and Facilities (i.e. Routes and Courses are out of scope).