[OisinKyne]

Sends a User-Agent: charon/<version> header on every Obol API request, so the API can attribute traffic. Today every Go client shows up as Go-http-client/1.1. The new WithUserAgent(product) client option lets tools built on this package put themselves in front, e.g. lido-dv-exit/v0.7.0 charon/v1.12.0.

httpPost, httpGet and httpDelete become Client methods so they can read the header from the client. PostFeeRecipientsFetch, which builds its own request, sets it too.

A 404 response to a POST now returns the new ErrLockNotFound sentinel, matched on status, not body text. The error keeps its status and body fields. Before, 404s were a generic http POST failed error, so callers couldn't tell "the cluster lock isn't published to this API" from a transient failure. lido-dv-exit retried such a cluster forever without telling the operator. PostFeeRecipientsFetch's existing "cluster is unknown to the API" error now wraps it too.

httpGet also closes the response body on non-2xx responses; the 404 path used to leak it.

category: feature
ticket: none

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

❌ Patch coverage is 76.92308% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.65%. Comparing base (4e4d996) to head (1186421).

Files with missing lines	Patch %	Lines
app/obolapi/feerecipient.go	0.00%	4 Missing ⚠️
app/obolapi/exit.go	66.66%	1 Missing ⚠️
app/obolapi/test.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4808      +/-   ##
==========================================
+ Coverage   67.61%   67.65%   +0.04%     
==========================================
  Files         254      254              
  Lines       33609    33622      +13     
==========================================
+ Hits        22725    22748      +23     
+ Misses      10883    10873      -10     
  Partials        1        1              

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