feat: introduce ToolSourceType enum and refactor related code to use it

internal/pkg/enums/tool.go

@@ -0,0 +1,24 @@
+package enums
+
+type ToolSourceType string
+
+const (
+	ToolSourceTypeMCP     ToolSourceType = "mcp"
+	ToolSourceTypeGraph   ToolSourceType = "graph"
+	ToolSourceTypeBuiltin ToolSourceType = "builtin"
+)
+
+var ToolSourceTypeValues = []ToolSourceType{
+	ToolSourceTypeMCP,
+	ToolSourceTypeGraph,
+	ToolSourceTypeBuiltin,
+}
+
+func IsValidToolSourceType(sourceType ToolSourceType) bool {
+	for _, item := range ToolSourceTypeValues {
+		if item == sourceType {
+			return true
+		}
+	}
+	return false
+}