Fix sentry-tower URL generation

[pbzweihander]

request.uri() may contains only relative URI (e.g. /foo/bar), but Url::parse requires full URL with base (e.g. http://localhost/foo/bar). So request.uri().to_string().parse() can fail.

This PR adds a fixed http:// scheme if the scheme does not exist and a host from the host header if the authority does not exist before parsing the URL.

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[codecov-commenter]

Codecov Report

Merging #460 (b6fae75) into master (2243fa5) will decrease coverage by 0.08%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #460      +/-   ##
==========================================
- Coverage   80.28%   80.19%   -0.09%     
==========================================
  Files          73       73              
  Lines        8389     8398       +9     
==========================================
  Hits         6735     6735              
- Misses       1654     1663       +9