[DRAFT] Upgrade procedure to Mattermost 3.0 after May 16

Back in March we discussed a change to unify user accounts for the May 16 release. Earlier in April, we also discussed the Web Service APIs changing for the May 16 release.

The changes are quite significant and to make the change clear to users we’re incrementing the product version number to “3.0” for the May 16 release.

Based on feedback from the previous forum discussion, we’re sharing upgrade instructions to 3.0 a few weeks ahead of release so the community knows what’s coming, and share comments, questions and feedback.

For deployments that use a single team, or that use multiple teams without duplicate accounts, the 3.0 upgrade should not be a significant change.

The 3.0 upgrade will have the most benefit for deployments with multiple teams using duplicate accounts, and there will be some manual migration steps required to get to that benefit.