R04. Improve the email notification for proposal valuators

[paarals]

Is your feature request related to a problem? Please describe.

Describe the solution you'd like When a valuator is selected to comment on a proposal in the backend system, the valuator receives an email notification including a link to the proposal in the backend system.

As a valuer, I would like to receive an email with a link directly to the individual proposal as i am assigne (nothing is currently sent in this case). Same as #12

Mock up

Does this issue could impact on users private data? No

Acceptance criteria

• [x] Improve the email notification for proposal valuators

Technical specifications https://github.com/openpoke/decidim/issues/18

Implementation

• [x] Initial solution: https://github.com/openpoke/decidim/pull/23
• [x] Final solution: https://github.com/openpoke/decidim/pull/25

Testing Steps to reproduce: https://letterbox.dev.pokecode.net/admin/participatory_processes/digital-letterbox/components/2/manage/

1. As a process-admin, I make new valuators in Process Admins

2. As a process-admin, I assign a valuator in one or more proposal

3. As a valuator, I received an email with assigned proposals to evaluate

Additional context Metadecidim proposal: https://meta.decidim.org/processes/roadmap/f/122/proposals/17113

[Naadjjaa]

@paarals Works, thank. Also the link is at the moment to the frontend not to the backend. We actually like that better!