Add callbacks for download and job complete

[MrCreosote]

Not sure if job complete is going to be needed, will delete if not

[codecov]

Codecov Report

Attention: Patch coverage is 73.68421% with 5 lines in your changes missing coverage. Please review.

Project coverage is 56.20%. Comparing base (f82c102) to head (46fc710).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
cdmtaskservice/routes.py	66.66%	4 Missing ⚠️
cdmtaskservice/app.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #132      +/-   ##
==========================================
+ Coverage   55.85%   56.20%   +0.35%     
==========================================
  Files          31       31              
  Lines        1837     1854      +17     
==========================================
+ Hits         1026     1042      +16     
- Misses        811      812       +1     

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[Tianhao-Gu]

👍