Add method to retrieve server base URL

Author: skylar-stark

springdoc-openapi-common/src/main/java/org/springdoc/core/OpenAPIService.java

@@ -808,6 +808,14 @@ public SecurityService getSecurityParser() {
 		return securityParser;
 	}
 
+	/**
+	 * Gets server base URL
+	 *
+	 * @return the server base URL
+	public String getServerBaseUrl() {
+		return serverBaseUrl;
+	}
+
 	@Override
 	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
 		this.context = applicationContext;