Fix: Username find is matching partially

packages/rocketchat-lib/server/models/Users.js

@@ -22,7 +22,7 @@ class ModelUsers extends RocketChat.models._Base {
 
 	findOneByUsername(username, options) {
 		if (typeof username === 'string') {
-			username = new RegExp(username, 'i');
+			username = new RegExp(`^${ username }$`, 'i');
 		}
 
 		const query = {username};

server/methods/getUsernameSuggestion.js

@@ -15,9 +15,7 @@ function usernameIsAvaliable(username) {
 		return false;
 	}
 
-	return !RocketChat.models.Users.findOneByUsername({
-		$regex: new RegExp(`^${ username }$`, 'i')
-	});
+	return !RocketChat.models.Users.findOneByUsername(username);
 }
 
 function generateSuggestion(user) {