Flux v1 automation migration guide

[squaremo]

There's a guide for setting image automation up from scratch. As a companion, to give people migrating from Flux v1 extra help, we should have a guide to how to set v2 automation up to work in the same way as v1 automation.

This needs to cover:

• how to construct the equivalent to automation annotations
• the equivalents to ignore (actually a sync annotation, but people use it in conjunction with automation), deautomate, and locking
• general advice on the process for changing a Flux v1 system over to Flux v2

[stefanprodan]

@squaremo isn't this done in #806 ?

[squaremo]

Fixed by #806.