application-membership.create: Update description to reflect that t…

…he user must already be a member of the organization

Change-type: patch

DOCUMENTATION.md

@@ -1372,7 +1372,7 @@ balena.models.application.membership.getAllByUser(123).then(function(memberships
 <a name="balena.models.application.membership.create"></a>
 
 ###### membership.create(options) ⇒ <code>Promise</code>
-This method adds a user to an application by their username.
+This method adds a user to an application by their username if they are a member of the organization.
 
 **Kind**: static method of [<code>membership</code>](#balena.models.application.membership)  
 **Summary**: Creates a new membership for an application  

src/models/application-membership.ts

@@ -225,7 +225,7 @@ const getApplicationMembershipModel = function (
 		 * @function
 		 * @memberof balena.models.application.membership
 		 *
-		 * @description This method adds a user to an application by their username.
+		 * @description This method adds a user to an application by their username if they are a member of the organization.
 		 *
 		 * @param {Object} options - membership creation parameters
 		 * @param {String|Number} options.application - application handle (string), or id (number)