refactor: drop the URL-based error classifier and hint lookups

Errors are named by the service call that failed: Classify,
NotFoundError and ConflictError at the call site. Remove the endpoint
parser that guessed the resource from the request path, and the
follow-up reads the explainer made at error time (repository state,
issue-vs-pull-request, the existing pull request's URL) together with
the credentialed transport each API error carried for them.

Calls that the endpoint parser covered and the services did not now
classify themselves: issues, pull requests, reviews, comments,
releases, branches, wiki pages, repositories, organizations and SSH
keys. Unclassified failures fall back to the generic
"not found (HTTP 404 GET ...)" text.

Signed-off-by: bircni <bircni@icloud.com>

internal/transport/client.go

@@ -35,8 +35,6 @@ type APIError struct {
 	// Instance is the installation URL the failed request was sent to, when it was recorded
 	// from a request.
 	Instance string
-	// lookup repeats reads on the failed request's instance with its credential.
-	lookup http.RoundTripper
 }
 
 func (e *APIError) Error() string {
@@ -68,24 +66,11 @@ func (e *APIError) request() string {
 	return strings.TrimSpace(fmt.Sprintf("HTTP %d %s %s", e.Status, e.Method, e.Endpoint))
 }
 
-// bind records the instance of the request to u and the credentialed transport rt, so the
-// failure can later be explained with LookupClient.
-func (e *APIError) bind(u *url.URL, rt http.RoundTripper) {
-	prefix, _, ok := strings.Cut(u.Path, "/api/v1/")
-	if !ok {
-		return
+// bind records the instance of the request to u.
+func (e *APIError) bind(u *url.URL) {
+	if prefix, _, ok := strings.Cut(u.Path, "/api/v1/"); ok {
+		e.Instance = (&url.URL{Scheme: u.Scheme, Host: u.Host, Path: prefix}).String()
 	}
-	instance := url.URL{Scheme: u.Scheme, Host: u.Host, Path: prefix}
-	e.Instance, e.lookup = instance.String(), rt
-}
-
-// LookupClient returns an HTTP client that repeats reads on the instance of the failed request,
-// Instance, with its credential, or nil when the error was not recorded from a request.
-func (e *APIError) LookupClient() *http.Client {
-	if e.lookup == nil {
-		return nil
-	}
-	return &http.Client{Transport: e.lookup, CheckRedirect: func(*http.Request, []*http.Request) error { return http.ErrUseLastResponse }}
 }
 
 const (