replaced functionCall with functionCalls (#137)

Co-authored-by: David Motsonashvili <davidmotson@google.com>
Co-authored-by: Rodrigo Lazo <rlazo@users.noreply.github.com>

.changes/common/bath-advertisement-attempt-car.json

@@ -0,0 +1 @@
+{"type":"MINOR","changes":["Add GenerateContentResponse#functionCalls and mark GenerateContentResponse#functionCall deprecated"]}

.changes/generativeai/badge-cake-arithmetic-cook.json

@@ -0,0 +1 @@
+{"type":"MINOR","changes":["Add GenerateContentResponse#functionCalls and mark GenerateContentResponse#functionCall deprecated"]}

generativeai/src/main/java/com/google/ai/client/generativeai/type/GenerateContentResponse.kt

@@ -33,10 +33,18 @@ class GenerateContentResponse(
   /** Convenience field representing the first text part in the response, if it exists. */
   val text: String? by lazy { firstPartAs<TextPart>()?.text }
 
-  /** Convenience field representing the first text part in the response, if it exists. */
+  /** Convenience field representing the first function call part in the request, if it exists */
+  @Deprecated("Use functionCallParts instead", ReplaceWith("functionCallParts"))
   val functionCall: FunctionCallPart? by lazy { firstPartAs() }
 
-  /** Convenience field representing the first text part in the response, if it exists. */
+  /** Convenience field to get all the function call parts in the request, if they exist */
+  val functionCalls: List<FunctionCallPart> by lazy {
+    candidates.first().content.parts.filterIsInstance<FunctionCallPart>()
+  }
+
+  /**
+   * Convenience field representing the first function response part in the response, if it exists.
+   */
   val functionResponse: FunctionResponsePart? by lazy { firstPartAs() }
 
   private inline fun <reified T : Part> firstPartAs(): T? {