Ci/aggressive linter

[bdmendes]

Closes #820
This sets up the very good analysis linter ruleset for the project, which enforces Dart's strict type-checking rules and more opinionated Flutter linting and formatting.
Although requiring a steeper adaptation to the project and the language, this will improve our consistency and allow for easier reviews and higher code quality overall.

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

[LuisDuarte1]

On this pr, I think it's appropriate to focus on making the linter pass without altering the app logic/architecture a lot. So, some rules were ignored that must be addressed in the future, and some calls to unawaited() (the linter requires that if you don't want to wait for the async function on a async context you must call this functions) that I don't know that are appropriate or not.

[bdmendes]

On this pr, I think it's appropriate to focus on making the linter pass without altering the app logic/architecture a lot. So, some rules were ignored that must be addressed in the future, and some calls to unawaited() (the linter requires that if you don't want to wait for the async function on a async context you must call this functions) that I don't know that are appropriate or not.

Absolutely

[bdmendes]

I have found that some things are still not ready, such as the test timing out and the course units page details not working. I'll draft this while these are not tackled, let me know if you find something @LuisDuarte1.

[bdmendes]

@LuisDuarte1 I can't reproduce the course units detail page being broken on develop, however, I made the parser stricter here and fixed a bug you had on the query parameters parser. Please let me know if it is fixed for you now

[Sirze01]

Haven't read thoroughly trough the code because of the large amount of changes. However, I tried to test every feature and submitted my feedback and correction suggestions to @bdmendes, who has already integrated them.

Good job all.

[Process-ing]

From what I have tested, the app looks to be working as it should and the code looks good. Great job!

P.S.: Rip double quote :')