docs: first draft for clientinfo endpoint (#3519)

docs/admin/auth-server/endpoints/clientinfo.md

@@ -1,17 +1,51 @@
 ---
 tags:
-  - administration
-  - auth-server
-  - endpoint
+- administration
+- auth-server
+- clientinfo
+- endpoint
 ---
 
-## This content is in progress
+# Overview
 
-The Janssen Project documentation is currently in development. Topic pages are being created in order of broadest relevance, and this page is coming in the near future.
+`/clientinfo` endpoint is an OAuth2 protected endpoint that is used to retrieve claims about registered client.
 
-## Have questions in the meantime?
+URL to access clientinfo endpoint on Janssen Server is listed in the response of Janssen Server's well-known
+[configuration endpoint](./configuration.md) given below.
 
-While this documentation is in progress, you can ask questions through [GitHub Discussions](https://github.com/JanssenProject/jans/discussion) or the [community chat on Gitter](https://gitter.im/JanssenProject/Lobby). Any questions you have will help determine what information our documentation should cover.
+```text
+https://janssen.server.host/jans-auth/.well-known/openid-configuration
+```
+
+`clientinfo_endpoint` claim in the response specifies the URL for clientinfo endpoint. By default, clientinfo endpoint looks
+like below:
+
+```
+https://janssen.server.host/jans-auth/restv1/clientinfo
+```
+
+Since clientinfo endpoint is an OAuth2 protected resource, a valid access token with appropriate scope is required to
+access the endpoint. More information about request and response of the clientinfo endpoint can be found in
+the OpenAPI specification of [jans-auth-server module](https://gluu.org/swagger-ui/?url=https://raw.githubusercontent.com/JanssenProject/jans/replace-janssen-version/jans-auth-server/docs/swagger.yaml#/Client_Info).
+
+## Disabling The Endpoint Using Feature Flag
+
+`/clientinfo` endpoint can be enabled or disable using [clientinfo feature flag](../../reference/json/feature-flags/janssenauthserver-feature-flags.md#clientinfo).
+Use [Janssen Text-based UI(TUI)](../../config-guide/tui.md) or [Janssen command-line interface](../../config-guide/jans-cli/README.md) to perform this task.
+
+When using TUI, navigate via `Auth Server`->`Properties`->`enabledFeatureFlags` to screen below. From here, enable or
+disable `clientinfo` flag as required.
+
+![](../../../assets/image-tui-enable-components.png)
+
+## Configuration Properties
+
+Clientinfo endpoint can be further configured using Janssen Server configuration properties listed below. When using
+[Janssen Text-based UI(TUI)](../../config-guide/tui.md) to configure the properties,
+navigate via `Auth Server`->`Properties`.
+
+- [clientInfoEndpoint](../../reference/json/properties/janssenauthserver-properties.md#clientinfoendpoint)
+- [mtlsClientInfoEndpoint](../../reference/json/properties/janssenauthserver-properties.md#mtlsclientinfoendpoint)
 
 ## Want to contribute?