Add 'Explain this code' assistant into the merge requests changes

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We could add an AiGenie component to merge request changes tab to explain parts of the changed files inline. This component has been already added to file blob view (but not enabled yet).

The benefits of this assistant are:

  1. It can unfold complex code structures for you and explain them step by step
  2. It can provide support for language built-in features without going into manual
  3. For non technical people it could make it easier to understand the code

Potential problems with this:

  1. Might be too early to see if it makes sense. We should potentially wait for the file view integration first.
  2. We need to have a context for added, removed and pre-existing lines. Could be addressed with some tuning added to the prompt, programmatically (exclude added lines from removed lines and vice versa) or both.
Edited by 🤖 GitLab Bot 🤖