We need to be able to identify self-intersections

[timlinux]

Problem

If a river layer's segments have self intersections, there should be a mechanism to identify all of these segments by extracting them to a new line layer.

Proposed solution

• [ ] @ismailsunni write a feature iterator that will test each line segment for the presence of self intersections (check the QGIS API - we already have logic for this).
• [ ] @ismailsunni for each identified segment write it to a new (memory layer)

  Expected outcome

• User should be able to extract all segments that have self intersections to a new layer.
• There is no expectation that we fix these issues (user will probably want to manually inspect and resolve).

[ismailsunni]

I think self intersection is for line, not for node. So, where do we put mark (or attribute) if the result is vector point layer? Same apply for #18

[timlinux]

@ismailsunni I updated the original issue description to make the requirements clearer. Please let me know if you need further info.

[ismailsunni]

segments is a line between a vertex right? If so, for this ticket, for each self intersection line, there will be two segments.