WebUI: Check for existing PR and update

[nkottary]

Needs: JuliaWeb/GitForge.jl#6

[codecov-io]

Codecov Report

Merging #163 into master will decrease coverage by 0.39%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master     #163     +/-   ##
=========================================
- Coverage   14.53%   14.14%   -0.4%     
=========================================
  Files          27       27             
  Lines        1156     1188     +32     
=========================================
  Hits          168      168             
- Misses        988     1020     +32

Impacted Files	Coverage Δ
src/webui/gitutils.jl	13.97% <0%> (-7.34%)	⬇️

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[christopher-dG]

The place that calls make_registration_request definitely is not expecting for an exception to be thrown... Places that throw exceptions should be returning the GitForge.result back to the caller. The @gf macro will handle logging the exception.