Added a debug file, vscode config to aid debugging in IDE

[3coins]

Added a debug file to allow server debugging by adding breakpoints directly within an IDE. Also, added a launch configuration for vscode that allows using the debugger interface within the IDE.

Notes

I wasn't able to extend this idea to debug the server code within a jupyterlab session. For example, this code did not engage the vscode debugger.

from jupyterlab.labapp import main

if __name__ == "__main__":
    main()

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[codecov-commenter]

Codecov Report

Merging #849 (468ab7e) into 1.x (8de001a) will decrease coverage by 0.02%. The diff coverage is 0.00%.

:exclamation: Current head 468ab7e differs from pull request most recent head 4f37177. Consider uploading reports for the commit 4f37177 to get more accurate results

@@            Coverage Diff             @@
##              1.x     #849      +/-   ##
==========================================
- Coverage   70.31%   70.28%   -0.03%     
==========================================
  Files          62       63       +1     
  Lines        7623     7626       +3     
  Branches     1259     1257       -2     
==========================================
  Hits         5360     5360              
- Misses       1882     1885       +3     
  Partials      381      381              

Impacted Files	Coverage Δ
jupyter_server/debug.py	0.00% <0.00%> (ø)

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[kevin-bates]

Hi @3coins - this is beneficial information - thank you for contributing this.

Rather than add this to the root level CONTRIBUTING.rst, I think this information is probably better suited in the Contributors Guide under Setting Up a Development Environment where other related information resides.

I don't think we should include (i.e., stop ignoring) any .vscode or debug.py files since those that do use VSCODE, will have their own copies of these files (although I'm not so sure about debug.py) and will need to either remove those files that are no longer "ignored" from their commits, or we'll see a replacement of those files from whoever was the last VSCODE contributor. I think this will also present problems to current VSCODE users when attempting to pull down the code as it will view their configurations as "unstaged changes". Instead, including the description of the launch.json file in the text should be sufficient.

Once relocated, I would be happy to add an entry for the PyCharm IDE, which will probably include a screenshot since its debug configurations are more detailed.

[3coins]

@kevin-bates Thanks for those suggestions. I will submit an update shortly.