UI/connectivity warning

[jcovaa]

Closes #528 //

Review checklist

• [ ] Terms and conditions reflect the current change
• [ ] Contains enough appropriate tests
• [ ] If aimed at production, writes a new summary in whatsnew/whatsnew-pt-PT
• [ ] Properly adds an entry in changelog.md with the change
• [ ] If PR includes UI updates/additions, its description has screenshots
• [ ] Behavior is as expected
• [ ] Clean, well-structured code

[jcovaa]

Some prints of the warning.

[thePeras]

I like the design. If the pharse was rephase to "Attention: No internet connection" would be better than demanding an action from the user. The user may be checking his next class, local data will be sufficient and no internet connection is required.

[jcovaa]

I liked more this design but it doesn't fit with some pages.
Edit: changed the phrase to "Attention: No internet connection" and "Atenção: Sem conexão à internet"

[jcovaa]

Some more design ideas

OR

[vitormpp]

The connectivity warning is outdated due to the ongoing redesign. It should be updated to match the current UI, or we may need to consider closing this PR.

[pedroafmonteiro]

Closed via #1695