added stats for student ages

[rono516]

This pull request adds statistics for student ages from ranges added in the config file

As seen above the number of students in various ages is displayed in the bar graph

The stats are also displayed in a table format to show all values which are not visible in the bar graph

[thdebay]

Thanks a lot @rono516 for this PR. It is looking really good. I will merge it as it is, since I've been able to test it and everything works. Since you asked for feedback, there are a couple of improvements I can think about (feel free to submit another PR if you want to add these points):

• it would be nice to have some unit tests to ensure the feature is working as it should and that the numbers are consistent with the data in the database

• from a business logic perspective, the graphs you created are based on the students from the students table (ie. all users registered in the system); it would also be interesting to have the ability to display the same graph per period. In that case, we would need to look at the enrollments table (in a similar way to what is done for the gender report). It would allow to get more details about the age distribution.

But the work you've done is already highly appreciated, thanks again!

[rono516]

Thanks so much for the feedback. I will work on these improvements and submit a PR as soon as I can.