feat: initial TTS support (#528)

* feat: initial TTS support

* chore: lint, omitempty

* chore: dont use pointer in struct

* fix: add mocked server tests to speech_test.go

Co-authored-by: Lachlan Laycock <supagroova@gmail.com>

* chore: update imports

* chore: fix lint

* chore: add an error check

* chore: ignore lint

* chore: add error checks in package

* chore: add test

* chore: fix test

---------

Co-authored-by: Lachlan Laycock <supagroova@gmail.com>

client_test.go

@@ -358,6 +358,9 @@ func TestClientReturnsRequestBuilderErrors(t *testing.T) {
 		{"ListRunSteps", func() (any, error) {
 			return client.ListRunSteps(ctx, "", "", Pagination{})
 		}},
+		{"CreateSpeech", func() (any, error) {
+			return client.CreateSpeech(ctx, CreateSpeechRequest{Model: TTSModel1, Voice: VoiceAlloy})
+		}},
 	}
 
 	for _, testCase := range testCases {