update merge student bussiness logic into one file

[fatchul]

Merged student domain into 1 service, because it will takes time to maintain if you separate per function per file. CMIIW

[restuwahyu13]

Thanks for your pull request @fatchul01, but if you're change services functionality, this app cannot be running, because these handlers I need services functionality, please check your pull request again. Thank you

[fatchul]

updated, I think repository better not use plural naming, and why did you create many repositories instead of 1 repo, such as result and results

[restuwahyu13]

Please check handler method before renewing the service, why I'm making repository into a small part, because if the project gets bigger, it'll be easy maintenance, and the name all depends on what each one wants