docs(internal): add comments

Author: kkweon

Diff for: internal/testutils/testutils.go

@@ -2,6 +2,8 @@ package testutils
 
 import "os"
 
+// MustExtractAPITokenFromEnv is a helper function that looks up PAPERSWITHCODE_API_TOKEN.
+// It panics if not found.
 func MustExtractAPITokenFromEnv() string {
 	apiToken, ok := os.LookupEnv("PAPERSWITHCODE_API_TOKEN")
 

Diff for: internal/transport/transport.go

@@ -9,11 +9,13 @@ type transportWithAuthHeader struct {
 
 var _ http.RoundTripper = transportWithAuthHeader{}
 
+// RoundTrip attaches "Authorization: Token <token>" for every request.
 func (t transportWithAuthHeader) RoundTrip(request *http.Request) (*http.Response, error) {
 	request.Header.Set("Authorization", "Token "+t.token)
 	return t.r.RoundTrip(request)
 }
 
+// NewTransportWithAuthHeader returns middleware that attaches "Authorization: Token <token>" header to every request.
 func NewTransportWithAuthHeader(token string) http.RoundTripper {
 	return transportWithAuthHeader{
 		r:     http.DefaultTransport,