Is there such a thing as Political Forgiveness, for example, to handle border disputes?
Yes, and this is sometimes called group forgiveness. Group forgiveness is different from one person forgiving another. In the latter, a person can change feeling, thoughts, and behaviors toward an offending other. Groups do not have feeling and thoughts (individuals within groups have the feeling and thoughts). So, only actions are part of group forgiveness such as proclamations of forgiveness or establishing norms within the group to try to be kind toward the other group as justice is pursued.
Here is the abstract of a journal article on this issue:
Enright, R.D., Lee, Y.R., Hirshberg, M.J., Litts, B.K., Schirmer, E.B., Irwin, A.J., Klatt, J., Hunt, J., & Song, J.Y. (2016). Examining group forgiveness: Conceptual and empirical issues. Peace and Conflict: Journal of Peace Psychology, 22, 153-162.