Add Content into Backend-Developer-Roadmap (#1583)

* Add Content into Backend-Developer-Roadmap 

Add content into Backend-developer-roadmap -> Learn about APIs -> Authentication

* Update authentication links

Co-authored-by: Kamran Ahmed <kamranahmed.se@gmail.com>

content/roadmaps/101-backend/content/109-apis/106-authentication/readme.md

@@ -1 +1,22 @@
-# Authentication
+# Authentication
+
+The API authentication process validates the identity of the client attempting to make a connection by using an authentication protocol. The protocol sends the credentials from the remote client requesting the connection to the remote access server in either plain text or encrypted form. The server then knows whether it can grant access to that remote client or not.
+
+Here is the list of common ways of authentication:
+
+- JWT Authentication
+- Token based Authentication
+- Session based Authentication
+- Basic Authentication
+- OAuth - Open Authorization
+- SSO - Single Sign On
+
+<ResourceGroupTitle>Free Content</ResourceGroupTitle>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://swoopnow.com/user-authentication/'>User Authentication: Understanding the Basics & Top Tips</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://betterprogramming.pub/how-do-you-authenticate-mate-f2b70904cc3a'>An overview about authentication methods</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://roadmap.sh/guides/sso'>SSO - Single Sign On</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://roadmap.sh/guides/oauth'>OAuth - Open Authorization</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://roadmap.sh/guides/jwt-authentication'>JWT Authentication</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://roadmap.sh/guides/token-authentication'>Token Based Authentication</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://roadmap.sh/guides/session-authentication'>Session Based Authentication</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://roadmap.sh/guides/basic-authentication'>Basic Authentication</BadgeLink>