UBER-953: Fix related issues

[haiodo]

Contribution checklist

Brief description

1. Allow to set default related issue target project, for related issues based on class of document, or based on space of related document.

2. Fix Create Lead Funnel selection.
3. Allow to post configure funnels with list of members.
4. Refactor model for tracker into separate files.

Checklist

• - UI test added to added/changed functionality?
• - Screenshot is added to PR if applicable ?
• - Does the code work? Check whether function and logic are correct.
• - Does Changelog.md is updated with changes?
• - Does the translations are up to date?
• - Does it well tested?
• - Tested for Chrome.
• - Tested for Safari.
• - Go through the changed code looking for typos, TODOs, commented LOCs, debugging pieces of code, etc.
• - Rebase your branch onto master and upstream branch
• - Is there any redundant or duplicate code?
• - Are required links are linked to PR?
• - Does new code is well documented ?

Related issues

A list of closed updated issues