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_test.go

@@ -213,30 +213,3 @@ func TestDebugRedactsOnlySensitiveQueryValues(t *testing.T) {
 		require.Equal(t, tc.redacted, sensitiveQuery(tc.path, tc.key), "%s %s", tc.path, tc.key)
 	}
 }
-
-func TestAPIErrorLookupRepeatsReadsWithTheFailedCredential(t *testing.T) {
-	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		require.Equal(t, "token secret", r.Header.Get("Authorization"))
-		require.Equal(t, "bob", r.Header.Get("Sudo"))
-		if r.URL.Path == "/base/api/v1/repos/a/b" {
-			_, _ = w.Write([]byte(`{"full_name":"a/b","has_issues":false}`))
-			return
-		}
-		w.WriteHeader(http.StatusNotFound)
-		_, _ = w.Write([]byte(`{"message":"not found"}`))
-	}))
-	defer server.Close()
-	client := New(server.URL+"/base", "secret", false)
-	client.Sudo = "bob"
-	_, err := client.Do(context.Background(), http.MethodGet, "repos/a/b/issues/9", nil, nil)
-	var apiErr *APIError
-	require.ErrorAs(t, err, &apiErr)
-	require.Equal(t, server.URL+"/base", apiErr.Instance)
-	lookup := apiErr.LookupClient()
-	require.NotNil(t, lookup)
-	resp, err := lookup.Get(server.URL + "/base/api/v1/repos/a/b")
-	require.NoError(t, err)
-	_ = resp.Body.Close()
-	require.Equal(t, http.StatusOK, resp.StatusCode)
-	require.Nil(t, (&APIError{Status: http.StatusNotFound}).LookupClient(), "errors built without a request cannot look up")
-}