Circuits: add termination: "Create and add another" is useless

[lucix-mich]

NetBox version

v2.11.9

Python version

3.8

Steps to Reproduce

1. Create a Circuit
2. In the newly created circuit, click "add" on either Termination A or Termination Z
3. The input mask provides a button "Create and add another" that opens the same input mask a second time, i.e. for the same termination side. But since circuits can only have one each of side A and side Z, the second input mask must (and will) lead to an error and is thus useless.

Expected Behavior

Button "Create and add another" not shown.

Observed Behavior

The input mask provides a button "Create and add another" that opens the same input mask a second time, i.e. for the same termination side. But since circuits can only have one each of side A and side Z, the second input mask must (and will) lead to an error and is thus useless.

[thatmattlove]

Since this is not a major bug, the fix for this is only going into 3.0 (currently in beta, but to be released soon). 9a8d33e should close this out.