Ruby on Rails plural (controller) and singular (model) convention - explanation
Solution 1:
Ruby on Rails follow linguistic convention. That means a model represents a single user, whereas a database table consists of many users.
Solution 2:
An instance of your User model represents a single user, so is singular. The users table, by contrast, holds all of your users, so it's plural.
Solution 3:
To complete Emily's answer
An instance of your User model represents a single user, so is singular. The users table, by contrast, holds all of your users, so it's plural.