Migration/Deprecation plan

[rido-min]

The existing Model Repo:

• UX https://devicemodels.azureiotsolutions.com/
• REST https://repo.azureiotrepository.com/Models/dtmi:azure:DeviceManagement:DeviceInformation;1?api-version=2020-05-01-preview
• CLI
• IoT Explorer

Will be shutdown when we start operating the new DMR. We need a plan to cover.

• Deprecation/Sunset dates
• Communicate to internal teams
• Migrate existing models in the public repo
• Provide options to save models in private repos
• Advertise the dates in the current UX/CLI/Explorer
• Communicate to existing users
• Identify breaking changes, and impact on existing customers

"As a customer who has previously used the model repository*, I understand what will happen to those models when the new repository goes live, and I know what steps I have to take (if any) to migrate to it."
* - Until now customers could ONLY use company repos, so this doesn't actually affect models in the public repo.