[FEATURE] Allow splitting calls party to a #dial
[FEATURE] Allow execution of split controllers when splitting a dial
[FEATURE] Dial#split should expose callback for main controller completion
[FEATURE] Allow rejoining calls after a split
[CS] Remove unused assignment
[BUGFIX] Call controller block's scope should be accessible
[BUGFIX] Avoid a silly spec race
[FEATURE] Support rejoining a Dial to a mixer
[FEATURE] Allow Dial#prep_calls to perform extra setup on calls

Yield to a passed block. Allows things like Matrioska listeners on outbound calls.
[FEATURE] Allow split callbacks on :others completion
[FEATURE] Allow merging dial operations together
[FEATURE] Include merged calls in dial status
[FEATURE] Don't unblock until after all merged calls leave a #dial
[FEATURE] Allow skipping cleanup of calls after a #dial

Allows outbound calls to continue after root call hangup
[BUGFIX] Unjoin all Dial parties before merging

Avoids join collisions
[BUGFIX] Log when skipping #dial cleanup
[BUGFIX] Ensure that when a dial root call ends after a merge, it unblocks everything
[CS] Better logging to assist tracing operations on Dial and call joins
[CS] Duplicate split/merge specs for #dial_and_confirm
Merge branch 'develop' into feature/complex_dial