[wip] Errors in sidebar enhancements

[xekc]

Current implementation

Concept designs

• Errors always shown on top

• Error text can be multi-line

• Many errors and informers can be stacked there (how much screen can hold vertically). Some will auto-hide, some will require to be manually closed.

Errors and notifications will be implemented in a very similar way so visual consistency and implementation quality are a key here. Error looks different, it stands out, it's almost a chat bubble, but clearly system-initiated chat.

Implementation

• Implement both LTR and RTL versions of errors.
• Test / tune support for multi-line error messages.
• Develop messages "stacking", closing of individual notifications.
• Improve errors in sidebar for Login interfaces.
• Password change interface errors notifications implementation / testing @xekc Password change as a (second) pilot sidebar interface #936

Testing

• A run on mobile testing, adjustments on mobile screens. @xekc