HSTTWO-4244 Create preview configuration for branches if absent
PS or partners might be used to or have a script that removes -preview configs during a new deployment, including preview configs of branches. For master branches the -preview config is already created automatically if it's missing, but for branch config not. Solve this by also recreating -preview config of the branches whenever master -preview config is recreated. The channel manager will call startEdit for the master before it switches to a branch, so it's safe to implement this in the MountResource#startEdit().
Showing with 55 additions and 17 deletions