[Feature] Configure business hour variables

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

- [X] I have searched the existing issues

### Describe the Feature

Currently business hours are only known to the end customer, making it difficult to perform end calculations between start and end time. Creating variables that allow the customer to configure business hours in dbt could result in more accurate calculations of a host of response time metrics.

Creating variables of `business_start_time_by_hour`, `business_end_time_by_hour` that end users could configure could provide more accurate data to our customers.

This will also probably require us to refactor our data models to account for these models, so we can more accurate measurements for median first response time and other valuable time-based calculations.

Note: Complexity increases significantly if business hours have to be configured by day and would have to be scoped out.

### Describe alternatives you've considered

Currently our data models do not account for business hours in a satisfactory manner, which likely prevents higher adoption of our Intercom data.

### 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_

The issue names no files, tests, or entry points. Start by mapping the dbt data models that calculate median first response time and identifying how customer-configurable variables are defined. Scope whether hours vary by day; done means configured business hours affect the relevant time-based metrics.

Written by the indexing model from the issue text.