refactor: cache user agent (#64)

client.go

@@ -55,6 +55,13 @@ func NewClient(opts ...Option) (Client, error) {
 	// Removes trailing / so it is easier later Host + URL
 	d.Host = strings.TrimSuffix(d.Host, "/")
 
+	// Formats the user agent
+	d.UserAgent = fmt.Sprintf(
+		"go-client-codegen/%s %s",
+		strings.TrimLeft(Version(), "v"),
+		strings.TrimSpace(d.UserAgent),
+	)
+
 	return newClient(d), nil
 }
 
@@ -133,14 +140,7 @@ func (d *aivenClient) do(ctx context.Context, method, path string, v any) (*http
 	}
 
 	req.Header.Set("Content-Type", "application/json")
-	req.Header.Set(
-		"User-Agent",
-		strings.TrimSpace(fmt.Sprintf(
-			"go-client-codegen/%s %s",
-			strings.TrimLeft(Version(), "v"),
-			d.UserAgent,
-		)),
-	)
+	req.Header.Set("User-Agent", d.UserAgent)
 	req.Header.Set("Authorization", "aivenv1 "+d.Token)
 
 	// TODO: BAD hack to get around pagination in most cases

client_test.go

@@ -51,6 +51,7 @@ func TestServiceCreate(t *testing.T) {
 		assert.NoError(t, err)
 		assert.Equal(t, "foo", expectIn.ServiceName)
 		assert.Equal(t, "kafka", expectIn.ServiceType)
+		assert.Regexp(t, `go-client-codegen/[0-9\.]+ unit-test`, r.Header["User-Agent"])
 
 		// Creates response
 		w.Header().Set("Content-Type", "application/json")
@@ -61,7 +62,7 @@ func TestServiceCreate(t *testing.T) {
 	defer server.Close()
 
 	// Points a new client to the server url
-	c, err := NewClient(TokenOpt("token"), HostOpt(server.URL))
+	c, err := NewClient(TokenOpt("token"), HostOpt(server.URL), UserAgentOpt("unit-test"))
 	require.NotNil(t, c)
 	require.NoError(t, err)