Invalid roll numbers registration sorted

[TirthGada]

Created a function in serialisers.py which checks the format of roll no starting from [18,19,20,21,22,23] as well as length and other roll no characteristics before creating a user object

[Prater-12]

You seem to have pushed a branch containing commits corresponding to issues other than the one you are making this PR for. You will need to make a PR containing only the commit corresponding to the check function.

A guide on how you can achieve this can be found here: #10 (comment)

[Prater-12]

Regarding the function itself, you have laid a foundation to how the problem can be approached. There are however some issues:

• While your solution seems to work for obviously invalid roll numbers, it does not work for some of the less easy to detect cases mentioned in the issue:
  • 23M9999, 20101010 (invalid roll numbers)
  • 26B1001 (roll numbers that are technically valid, but of future batches)
• Especially for applications that will remain in use for a long time with many dynamic parts, one should avoid hard-coding and magic numbers as much as possible. Having a static list [18,19,20,21,22,23] is a bit. You can try using one latest_batch variable that you set (to 23 in this case), and generate the list based on this value.