Show exercise names in gym mode navigation

[mohammadrafigh]

Proposed Changes

• Fetch exercise names from provider instead of showing ids in gym mode navigation dialog

Related Issues (if applicable)

• Instead of showing exercise names the app shows exercise id #297

Please check that the PR fulfills these requirements

• Set a 100 character limit in your editor/IDE to avoid white space diffs in the PR
• Tests for the changes have been added (for bug fixes / features)
• Added yourself to AUTHORS.md

[rolandgeider]

Now that I'm looking at the code. Wouldn't it be easier if we modified _exercisePages? Right now it is basically only a list that contains the UUID and the position. We could convert it e.g. to a Map<ExerciseBase, int> and this would allow us to even show the exercise image in the dropdown (don't know if this would be a good idea UX wise, but we would have the possibility)

[mohammadrafigh]

@rolandgeider yes sure, I did this first, but I got some exceptions due to unknown Map types. I know I should somewhere define a fromJson for that type to work but since I'm a newbie on Dart so avoided that :D. I will take a look again and try to go that way.

[rolandgeider]

we don't need to convert to json, we should be able to just put the whole object there. But if this makes problems, we can just use your approach