Add getI() method to DanglingLine's boundary

[caioluke]

Please check if the PR fulfills these requirements

• [X] The commit message follows our guidelines
• [X] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce?

Feature

What is the current behavior?

Boundary nodes do not have a getI() method, whereas terminals do. Therefore, for paired dangling lines, we can not get the current from both sides of the half line easily.

What is the new behavior (if this is a feature change)? Add the getI() method for boundary nodes.

Does this PR introduce a breaking change or deprecate an API?

• [X] Yes
• [ ] No

If yes, please check if the following requirements are fulfilled

• [X] The Breaking Change or Deprecated label has been added
• [X] The migration steps are described in the following section

What changes might users need to make in their application due to this PR? (migration steps)

Add the getI() method for the Boundary implementations.

[sonarcloud[bot]]

Quality Gate failed

Failed conditions
64.3% Coverage on New Code (required ≥ 80%)

See analysis details on SonarCloud