created the manual client for tavern so we can change callback url

[Cictrone]

What type of PR is this?

/kind feature

What this PR does / why we need it:

So we have some control over callback URL.

[codecov]

Codecov Report

Attention: 74 lines in your changes are missing coverage. Please review.

Comparison is base (e59b69b) 71.46% compared to head (4df4924) 71.01%.
Report is 6 commits behind head on main.

Files	Patch %	Lines
implants/lib/c2/src/c2_manual.rs	0.00%	68 Missing ⚠️
implants/imix/src/tasks.rs	0.00%	3 Missing ⚠️
implants/imix/src/main.rs	0.00%	2 Missing ⚠️
tavern/app.go	50.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #457      +/-   ##
==========================================
- Coverage   71.46%   71.01%   -0.45%     
==========================================
  Files         118      119       +1     
  Lines        9003     9081      +78     
==========================================
+ Hits         6434     6449      +15     
- Misses       2446     2509      +63     
  Partials      123      123              

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