Validate DD_TRACE_AGENT_URL

[bwoebi]

This avoids panics in the sidecar and crashes in crashtracker initialization.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.00%. Comparing base (7a0d358) to head (b9efbb8).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3050      +/-   ##
============================================
- Coverage     73.06%   73.00%   -0.06%     
  Complexity     2787     2787              
============================================
  Files           139      139              
  Lines         15272    15272              
  Branches       1043     1043              
============================================
- Hits          11158    11150       -8     
- Misses         3563     3571       +8     
  Partials        551      551              

Flag	Coverage Δ
appsec-extension	68.41% <ø> (ø)
tracer-php	74.77% <ø> (-0.08%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

see 2 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7a0d358...b9efbb8. Read the comment docs.

[iamluc]

LGTM, but shouldn't we fix ddog_endpoint_from_url instead?

[bwoebi]

@iamluc Possibly, but maybe they also don't want auto-fallback to http. PHP has that auto-fallback since a long time in the background sender (curl does it for us). Hence I mirrored this here too.