Add how to define new endpoints in web for api-versioning.md

rfd/0179-api-versioning.md

@@ -146,6 +146,37 @@ func (h *Handler) getFoos() (interface{}, error) {
 }
 ```
 
+#### Defining new endpoints in the web client
+All endpoints should be defined in a JS object, similary done [here](https://github.com/gravitational/teleport.e/blob/ebf079267020d59f14353dd3495b4fd783339fa5/web/teleport/src/config.ts#L134).
+
+This helps us tell apart same paths but with different HTTP verbs.
+
+Example of a new single endpoint:
+
+```ts
+user: {
+  create: '/v1/webapi/users',
+}
+```
+
+Example of an endpoint with same paths but with different verbs:
+
+```ts
+user: {
+  create: '/v1/webapi/users',
+  update: '/v1/webapi/users',
+}
+```
+
+Example of creating a version N endpoint:
+```ts
+user: {
+  // TODO(<your-github-handle>): DELETE IN 18.0 - replaced by /v2/webapi/users
+  create: '/v1/webapi/users',
+  createV2: '/v2/webapi/users',
+}
+```
+
 ### Removing an endpoint
 An endpoint can be removed in a major version n+2, where n is the last major
 version where the endpoint was used.
@@ -269,4 +300,4 @@ tab was available in clients that _may_ have been communicating with proxies
 older than the required version. So a check was made to see if that proxy
 supported pinned resources, and if it wasn't, made the error known to the user
 that "Pinned Resources is supported by proxies version 14.1+" (or something like
-that).
+that).