Docs: Describe applying a license (#55078)

* Docs: Describe adding a license via API

* Add missing word

docs/sources/developers/http_api/licensing.md

@@ -59,6 +59,66 @@ Status codes:
 
 - **200** - OK
 
+## Add license
+
+> **Note:** Available in Grafana Enterprise v7.4+.
+
+`POST /api/licensing/token`
+
+Applies a license to a Grafana instance.
+
+**Required permissions**
+
+See note in the [introduction]({{< ref "#enterprise-license-api" >}}) for an explanation.
+
+| Action          | Scope |
+| --------------- | ----- |
+| licensing:write | n/a   |
+
+### Examples
+
+**Example request:**
+
+```http
+POST /licensing/token
+Accept: application/json
+Content-Type: application/json
+Authorization: Bearer eyJrIjoiT0tTcG1pUlY2RnVKZTFVaDFsNFZXdE9ZWmNrMkZYbk
+
+{"token":"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ0aGlzIjoiaXMiLCJub3QiOiJhIiwidmFsaWQiOiJsaWNlbnNlIn0.bxDzxIoJlYMwiEYKYT_l2s42z0Y30tY-6KKoyz9RuLE"}
+```
+
+**Example response:**
+
+```http
+HTTP/1.1 200 OK
+Content-Type: application/json
+Content-Length: 357
+
+{
+  "jti":"2",
+  "iss":"https://grafana.com",
+  "sub":"https://play.grafana.org/"
+  "lid":"1",
+  "included_users":15,
+  "lic_exp_warn_days":30,
+  "tok_exp_warn_days":2,
+  "update_days":1,
+  "prod":["grafana-enterprise"],
+  "company":"Grafana Labs"
+}
+
+```
+
+The response is a JSON blob available for debugging purposes. The
+available fields may change at any time without any prior notice.
+
+Status Codes:
+
+- **200** - OK
+- **400** - Bad request
+- **500** - Internal server error (refer to server logs for more details)
+
 ## Manually force license refresh
 
 > **Note:** Available in Grafana Enterprise v7.4+.
@@ -100,8 +160,7 @@ Content-Length: 357
   "iss":"https://grafana.com",
   "sub":"https://play.grafana.org/"
   "lid":"1",
-  "included_admins":5,
-  "included_viewers":10,
+  "included_users":15,
   "lic_exp_warn_days":30,
   "tok_exp_warn_days":2,
   "update_days":1,