Add a system Binding for current Signed in user

Having ability to use the current Signed in user is beneficial in cases where we can ensure it is the right person/role in the form, overriding potential dead branches and generally to be precise with conditional actions.

Case scenario:

• Owner transitions into Review status

• Reviewer can review, comment back or approve back to Owner.

• Owner can see the Review state.

• Owner wants to progress without Reviewer approval

• Transition is formulated based on condition that the current Signed In User is part of the Owner Role.