ref: ED023

User story

Is your feature request related to a problem? Please describe.
As a participant/admin I miss some notifications on the platform.

Describe the solution you'd like

Add missing action notifications (define texts)

• Notify participants that there's a new comment by a group
• Notify participants that have been invited as members of an assembly
• Notify admin that a group has been created
• Notify admin that a group has updated its profile and has been left unverified
• Notify admin that an initiative is pending of technical validation
• Notify process admins and valuators when someone leaves a private note on a proposal

Additional context
https://meta.decidim.org/processes/roadmap/f/122/proposals/13284

Does this issue could impact on users private data?
No

Acceptance criteria

• As a participant I receive a notification when there's a new comment by a group
• As a participant I receive a notification when I've been invited as a member of an assembly
• As an admin I receive a notification when a group has been created
• As an admin I receive a notification when a group has updated its profile and has been left unverified
• As an admin I receive a notification when an initiative has been sent to Technical Validation
• As an admin I receive a notification when someone leaves a private note on a proposal
• As a valuator I receive a notification when someone leaves a private note on a proposal