Make "user" the default role. (#67)

Instead of leaving it empty, we should default to "user".

---------

Co-authored-by: Daymon <[email protected]>

.changes/branch-badge-dock-advertisement.json

@@ -0,0 +1 @@
+{"type":"MAJOR","changes":["Make \"user\" the default role in all requests"]}

generativeai/src/main/java/com/google/ai/client/generativeai/Chat.kt

@@ -73,7 +73,7 @@ class Chat(private val model: GenerativeModel, val history: MutableList<Content>
    * @throws InvalidStateException if the [Chat] instance has an active request.
    */
   suspend fun sendMessage(prompt: String): GenerateContentResponse {
-    val content = content("user") { text(prompt) }
+    val content = content { text(prompt) }
     return sendMessage(content)
   }
 
@@ -84,7 +84,7 @@ class Chat(private val model: GenerativeModel, val history: MutableList<Content>
    * @throws InvalidStateException if the [Chat] instance has an active request.
    */
   suspend fun sendMessage(prompt: Bitmap): GenerateContentResponse {
-    val content = content("user") { image(prompt) }
+    val content = content { image(prompt) }
     return sendMessage(content)
   }
 
@@ -150,7 +150,7 @@ class Chat(private val model: GenerativeModel, val history: MutableList<Content>
    * @throws InvalidStateException if the [Chat] instance has an active request.
    */
   fun sendMessageStream(prompt: String): Flow<GenerateContentResponse> {
-    val content = content("user") { text(prompt) }
+    val content = content { text(prompt) }
     return sendMessageStream(content)
   }
 
@@ -162,7 +162,7 @@ class Chat(private val model: GenerativeModel, val history: MutableList<Content>
    * @throws InvalidStateException if the [Chat] instance has an active request.
    */
   fun sendMessageStream(prompt: Bitmap): Flow<GenerateContentResponse> {
-    val content = content("user") { image(prompt) }
+    val content = content { image(prompt) }
     return sendMessageStream(content)
   }
 

generativeai/src/main/java/com/google/ai/client/generativeai/internal/api/shared/Types.kt

@@ -40,7 +40,7 @@ internal enum class HarmCategory {
 
 typealias Base64 = String
 
-@Serializable internal data class Content(val role: String? = null, val parts: List<Part>)
+@Serializable internal data class Content(val role: String? = "user", val parts: List<Part>)
 
 @Serializable(PartSerializer::class) internal sealed interface Part