This stylelint-scss rule is useful because we were inconsistent when
using calc(); sometimes we added interpolation to Sass variables, and
sometimes we didn't. The reason why we originally added interpolation
was that it was necessary until we migrated to Dart Sass in commit
d54971e53. Since then, we can omit the interpolation, which is also what
the Sass documentation recommends [1].
[1] https://sass-lang.com/documentation/values/calculations/
We hadn't added this rule before because there was no such rule in
scss-lint. Instead, we were following it without a linter, and so we
unintentionally broke it sometimes.
But now we're using Stylelint, so we can add the rule and let the linter
check we're still following it.
The division operator `/` from Sass is deprecated because `/` is used in
CSS for uses other than dividing numbers. That's why we were getting
many warnings like:
```
Deprecation Warning: Using / for division outside of calc() is
deprecated and will be removed in Dart Sass 2.0.0.
Recommendation: math.div($line-height, 2) or calc($line-height / 2)
More info and automated migrator: https://sass-lang.com/d/slash-div
margin-top: $line-height / 2;
```
Since using math.div makes the code harder to read and `calc` is
universally supported by all browsers (although the implementation in
Internet Explorer doesn't work in certain cases), we're using `calc`
when assigning the value to a CSS property.
However, we're also using divisions when assigning Sass variables, and
in those cases using `calc` is trickier because sometimes these
variables are used in other operations. We'll handle these cases in the
next commit.
This way we make it easier to modify.
Note that, since the title of the page is "Administration" and it's in
the "Admin" section, we're adding an option to the `header` method in
order to avoid having a confusing title like "Administration - Admin".
Also note that, by removing the `title` HTML class, we avoid inheriting
styles from the `dashboard.scss` stylesheet, and now the heading is
displayed in the position it was meant to.
Finally, the concept of using a `main-class` for the current page comes
from a branch (currently in development) which will replace the <div>
tag with the `admin-content` class with a `main` tag.
