feat: Added Microservices UI Client side composition #2698 (#3062)

* Added Microservices client side ui composition to the repo.
Added ClientSideCompositionTest, ApiGateway, ClientSideIntegrator, FrontendComponent, CartFrontend, ProductFrontend, updated pom.xml, ReadME.md.

* Improved some checkstyle changes.

* Added Random variable to re-use the random instead of creating it everytime in FrontendComponent.

* changed the Pom.xml and upadted the ReadME.md

* Changes in the README.md File as per requirement, name of the file changed from ReadME.md to README.md

---------

Co-authored-by: Ilkka Seppälä <iluwatar@users.noreply.github.com>

microservices-client-side-ui-composition/etc/client-side-ui-composition.urm.puml

@@ -0,0 +1,31 @@
+@startuml client_side_ui_composition_updated
+skinparam classAttributeIconSize 0
+
+class ApiGateway {
+    +registerRoute(path: String, component: FrontendComponent)
+    +handleRequest(path: String, params: Map<String, String>): String
+}
+
+class FrontendComponent {
+    +fetchData(params: Map<String, String>): String
+    #getData(params: Map<String, String>): String
+}
+
+class ProductFrontend {
+    +getData(params: Map<String, String>): String
+}
+
+class CartFrontend {
+    +getData(params: Map<String, String>): String
+}
+
+class ClientSideIntegrator {
+    +composeUI(path: String, params: Map<String, String>)
+}
+
+ApiGateway --> FrontendComponent
+FrontendComponent <|-- ProductFrontend
+FrontendComponent <|-- CartFrontend
+ClientSideIntegrator --> ApiGateway
+
+@enduml