feat(client-configuration): add proxy configuration in client configuration interface

Author: hamzamahmood

src/main/java/io/apimatic/coreinterfaces/http/ClientConfiguration.java

@@ -1,5 +1,6 @@
 package io.apimatic.coreinterfaces.http;
 
+import io.apimatic.coreinterfaces.http.proxy.ProxyConfiguration;
 import java.util.Set;
 
 /**
@@ -73,4 +74,12 @@ public interface ClientConfiguration {
      * @return a copy of skipSslCertVerification
      */
     boolean skipSslCertVerification();
+
+    /**
+     * Retrieves the proxy configuration containing the address, port, and optional credentials
+     * used to connect through a proxy server.
+     *
+     * @return the {@link ProxyConfiguration} instance if no proxy is configured
+     */
+    ProxyConfiguration getProxyConfiguration();
 }

src/main/java/io/apimatic/coreinterfaces/http/proxy/ProxyConfiguration.java

@@ -0,0 +1,32 @@
+package io.apimatic.coreinterfaces.http.proxy;
+
+public interface ProxyConfiguration {
+
+    /**
+     * Returns the address (hostname or IP) of the proxy server.
+     *
+     * @return the proxy server address as a {@link String}
+     */
+    String getAddress();
+
+    /**
+     * Returns the port number on which the proxy server is listening.
+     *
+     * @return the proxy server port
+     */
+    int getPort();
+
+    /**
+     * Returns the username used for proxy authentication.
+     *
+     * @return the proxy authentication username as a {@link String}
+     */
+    String getUsername();
+
+    /**
+     * Returns the password associated with the proxy authentication username.
+     *
+     * @return the proxy authentication password as a {@link String}
+     */
+    String getPassword();
+}