Added API for developer stastics showing domain frequency for each developer

[abdulrahim2002]

The API get_developer_stats fetches the closed issues, applies the random forest algorithm on them to obtain the domain labels for each of the closed issue. Furthermore, it gets the developer associated with the closed issue from the { "user", "login" } and { "user", "id" } parameters in returned JSON.

Then it builds a dataframe in the form:

------------------------------------------------------ 
| developer_name | developer_id | domain | frequency | 
------------------------------------------------------

Which tells us, how much issues, a particular developer has solved on a particular domain. This information is helpful to determine the expertise of a developer. For example, a developer who has solved many issues relating to 'database' can be assumed to be an expert in all issues that pertain to the 'database' label on that particular repository.

[abdulrahim2002]

Sample output:

developer_name	developer_id	Domain	frequency
wanling0000	164749591	Data Structure-Data Sorting	1
wanling0000	164749591	Event Handling	1
wanling0000	164749591	Software Development and IT Operations-Configuration Management	1
tim-bsm	125408219	Application-Version Control	1
tim-bsm	125408219	Databases-Backup and Recovery	1
tim-bsm	125408219	Software Development and IT Operations-Configuration Management	1
subhramit	74734844	Event Handling	16
subhramit	74734844	Software Development and IT Operations-Configuration Management	16
subhramit	74734844	Data Structure-Data Sorting	14
subhramit	74734844	Data Structure-Search Algorithms	2
priyanshu16095	147549268	Data Structure-Data Sorting	1

[abdulrahim2002]

Sample input:

{
    "github_token": "#github token",
    "repo_owner": "JabRef",
    "repo_name": "JabRef",
    "openai_key": "#open ai api key",
    "limit" : "100"
}

[BenCarter44]

Hello Abdul,

Thank you for submitting the PR. Sorry there has not been any comments way sooner! Got busy with other things :) . Nice feature on adding developer statistics, it will make a great addition to the CoreEngine. I noticed you overwritten the Issue class as well as redefining the get_issues() function.

I think your changes would work better in the actual Issue class in src/issue_class.py, where the optional attributes dev_name and dev_id are included in the original Issue class with the optional attributes. Same goes for the get_issues() class. From what I read, it is the same function except for using the new Issue() class. Therefore, I think your changes would work better in the original get_issues() function, located in src/classifier.py. The function get_developer_stats can remain in the file named correspondingly.

There should not be any negative effects on the rest of the program as these new optional attributes in the Issue class are just for generating statistics from get_developer_stats.

With these two small changes, then it would be ready to merge.

If you need anything you can leave a comment.

-Ben