Use AJV, refactor a lot

api/models/users/schemas.js

@@ -0,0 +1,19 @@
+const sharedSchemas = require(`../schemas`);
+
+module.exports = {
+	"create": {
+		"$schema": "http://json-schema.org/draft-07/schema#",
+		"title": "Create User",
+		"description": "An object to create a new user",
+		"type": "object",
+		"properties": {
+			"email": sharedSchemas.email,
+			"password": {
+				"type": "string",
+				"minLength": 10,
+				"maxLength": 50
+			}
+		},
+		"required": ["email", "password"]
+	}
+};