[Feature] Add month spine to monthly recurring revenue model

### Is there an existing feature request for this?

- [X] I have searched the existing issues

### Describe the Feature

Currently our monthly recurring revenue does not have a monthly spine associated with it, pulling data directly from account overview and balance transaction models. That can lead to no monthly data for months with no transactions associated with an account.

### Describe alternatives you've considered

_No response_

### Are you interested in contributing this feature?

- [X] Yes.
- [ ] Yes, but I will need assistance and will schedule time during your [office hours](https://calendly.com/fivetran-solutions-team/fivetran-solutions-team-office-hours) for guidance.
- [ ] No.

### Anything else?

_No response_