Add UserAnswers model and DB schema to orm.js

[alodahl]

A a new model in orm.js based on this definition

user_answers table / UserAnswers model

All of these columns are NOT NULL unless otherwise specified.

• id: primary key / integer sequence
• user_id: string (foreign key to users.id)
• question_number: integer
• is_correct: boolean
• elapsed_time_ms: integer
• created_at : timestamp (we don't need updated_at since this is immutable. this name can be configured in the sequelize model as we don't want the default camel case name)

Please use the sequelize docs

[ambikasadhu1101]

I'd like to work on this