[Feature]Be notified when the UNBONDING > UNBONDED period has ended

[cristianmalfesi]

Estimated time: to define
To Do:
 Delegators, after unbond the delegate, there is a period of 7 days/rounds that he must wait before to bond to a new delegate.
We need to add a new alert that sends a message to the user informing when unBound period is ended and Delegator can bond again.

Acceptance Criteria:

• Delegator unBound the Delegate
• UnBond period start
• After 7 days/rounds the Delegator receives an email informing the period is ended and he can bond again.
   
  Links and resources: