[Lava-announce] Release schedules

We've done a little bit of advance planning and there are now three milestones which developers will be using to schedule upcoming releases.

https://git.lavasoftware.org/groups/lava/-/milestones

Issues and merge requests have been assigned to the relevant milestone.

All dates are approximate.

We will also be announcing (here) when the next release would include database migrations so that admins have more notice of scheduled downtime. When a milestone includes database migrations, other changes which also include a database migration will be moved to that milestone so that admins can minimise total downtime.

The next release is expected to include the changes from the 2018.12 milestone.

The 2019.02 milestone already includes database migrations.