Forecast page allows programs to be entered that aren't part of Epic

Issue Summary

Users can associate additional unrelated programs to the Forecast tab of Portfolio Epic by adding some capacity to the Epic from the Forecast grid page.

Steps to Reproduce

1. Make sure to configure the Tier1 filter with a Portfolio containing Epics and Program Increments associated with multiple programs.
2. Go to the Forecast grid from the left navigation Programs > Manage > Forecast
3. Choose the default View Type: Agile by Program
4. Expand the Program increment List
5. Select/Click an Epic from the list
6. Verify what the current Primary Program is set to
7. Go to the Forecast tab and verify that the same program is visible and no other programs are available for selection in the Programs working on this Epic field for the Program Increment
8. Go to the Forecast page and add some capacity to a different program (not listed on Portfolio Epic).
   It allows the update (which it shouldn't even allow to add a capacity since the program hasn't been assigned to the Portfolio Epic).
9. Open the Portfolio Epic look at the Details tab. Notice the additional program was not added.
10. Open the Forecast tab and you will notice the additional program has automatically been added.
11. Remove the capacity on the Forecast grid page.
12. Go back into the Epic and notice the additional program was not removed from the Forecast tab.

See the following recording:

Expected Results

If you allow adding capacity to the Epic from the Forecast grid page, it should not only add the program to the Forecast tab of the Epic but as well to the Additional programs field of the Details tab.
If you remove the capacity from the Forecast grid page, it should as well remove the program from the Forecast tab of the Epic

Actual Results

You are allowed to add a capacity although the program hasn't been assigned to the Portfolio Epic.
The additional program was not removed from the Forecast tab when you remove the capacity from the Forecast grid page.

Workaround

Currently, there is no known workaround for this behavior. A workaround will be added here when available