New endpoint to return existing goals

We want to speed up the process of applying for mentorships by pulling the current goals from the mentee and populate the form application.

We need a new endpoint that returns the current goals for the given user, if there are no goals defined we are going to set a few common goals to pre-fill the application.

Request:
```
GET /users/${user.id}/goals
```

Response:
```
{
data: {
goals: [
{ id: number, description: string }
],
expectation: string,
background: string
}
}
```

**AC**
- Model the data for goals in mongo
- Read the current data from the database
- If there are no goals we need to send default goals (static for now)
- Return the data