Create schedule spine incorporating timezones and daylight time

[fivetran-jamie]

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fivetran made PR

What change(s) does this PR introduce?

• adjusts circleci testing to be a bit more thorough
• creates schedule spine model that incorporates timezones and daylight time stuff. down the line, when calculcating ticket metrics, we will determine which schedule to use based on the schedule_id it is associated with and what schedule (ie PT vs PST) is active when the ticket is active (wondering how to define this though, like do we pin the ticket on its creation date? what if a ticket is created a day before Daylight Savings starts or ends?)
• incorporates the schedule spine into the business hours models
• regenerate docs

Does this PR introduce a breaking change?

• Yes (please provide breaking change details below.)
• No (please provide explanation how the change is non breaking below.)

Is this PR in response to a previously created Issue

• Yes, Issue BUG - UTC Timezones for schedules need to be reworked #62
• No

How did you test the PR changes?

• CircleCi
• Other (please provide additional testing details below)
  testing locally

Select which warehouse(s) were used to test the PR

• BigQuery
• Redshift
• Snowflake
• Postgres
• Databricks
• Other (provide details below)

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Feedback

We are so excited you decided to contribute to the Fivetran community dbt package! We continue to work to improve the packages and would greatly appreciate your feedback on our existing dbt packages or what you'd like to see next.

[fivetran-joemarkiewicz]

See my comments inline

[fivetran-jamie]

flagging that i didn't add changelog stuff since that appears to the be in the release branch already? or i will add stuff after this PR is merged there...

[fivetran-jamie]

reminder to change packages.yml

[fivetran-joemarkiewicz]

Looks good! Just be sure to add the CHANGELOG