Create the function declaration schema at construction time

By creating the schema earlier, any errors when declaring the schema
will be caught at the declaration site, which makes debugging much easier.

Author: rlazo

firebase-vertexai/src/main/kotlin/com/google/firebase/vertexai/internal/util/conversions.kt

@@ -153,16 +153,7 @@ internal fun Tool.toInternal() =
   com.google.firebase.vertexai.common.client.Tool(functionDeclarations.map { it.toInternal() })
 
 internal fun FunctionDeclaration.toInternal() =
-  com.google.firebase.vertexai.common.client.FunctionDeclaration(
-    name,
-    description,
-    Schema(
-      properties = parameters.mapValues { it.value.toInternal() },
-      required = parameters.keys.minus(optionalParameters.toSet()).toList(),
-      type = "OBJECT",
-      nullable = false,
-    ),
-  )
+  com.google.firebase.vertexai.common.client.FunctionDeclaration(name, "", parameters.toInternal())
 
 internal fun com.google.firebase.vertexai.type.Schema.toInternal(): Schema =
   Schema(

firebase-vertexai/src/main/kotlin/com/google/firebase/vertexai/type/FunctionDeclaration.kt

@@ -41,4 +41,7 @@ class FunctionDeclaration(
   val description: String,
   val parameters: Map<String, Schema>,
   val optionalParameters: List<String> = emptyList(),
-)
+) {
+  private val schema: Schema =
+    Schema.obj(properties = parameters, optionalProperties = optionalParameters, nullable = false)
+}

firebase-vertexai/src/main/kotlin/com/google/firebase/vertexai/type/Schema.kt

@@ -130,14 +130,20 @@ internal constructor(
       optionalProperties: List<String> = emptyList(),
       description: String? = null,
       nullable: Boolean = false,
-    ) =
-      Schema(
+    ): Schema {
+      if (!properties.keys.containsAll(optionalProperties)) {
+        throw IllegalArgumentException(
+          "All optional properties must be present in properties. Missing: ${optionalProperties.minus(properties.keys)}"
+        )
+      }
+      return Schema(
         description = description,
         nullable = nullable,
         properties = properties,
         required = properties.keys.minus(optionalProperties.toSet()).toList(),
         type = "OBJECT",
       )
+    }
 
     /**
      * Returns a schema for an array.