New model for a purchase order reporting structure

[DJFresh66]

Are you a current Fivetran customer?
Doug Jeffery, Modulous

What change(s) does this PR introduce?
Adds required model for a purchase order reporting structure (follows the invoice model 'pattern')

Does this PR introduce a breaking change?

• Yes (please provide breaking change details below.)
• No - New models only, existing models are untouched

Is this PR in response to a previously created Issue

• Yes, Issue FEATURE - [Add Purchase Orders to Xero packages] #21
• No

How did you test the PR changes?

• CircleCi
• Other Using Fivetran transformations against our live Xero synch, manual tests in SQL to validate the volume and contents of the reporting table versus the source tables and the raw data. Also created a detailed download CSV and summary CSV which was QA'd against Xero by my internal customer (our CFO)

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

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

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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]

@DJFresh66 the updates you are suggesting in this PR make sense and look great to me! Before we can merge this into the next release branch, I have a quick request from you, and a few notices as to what I will change before release.

One request for you to add

• For our CircleCi testing we require a dummy csv table for the new source models you are adding. Would you be able to add two dummy csv tables to the integration_tests/seeds location. Here is a good example of what we are looking for.

Changes I will make once the seed data is added

• Apply a variable for users to enable the purchase order models. I checked and it seems only 40% of Xero users have these models. Therefore, we will want to disable them by default and allow users to enable them if they would like.
• Keep the versioning to be within dbt v1. Since the latest version of the package is compatible with dbt v1, we do not want to decrease the dbt range.

[DJFresh66]

Hi @fivetran-joemarkiewicz sorry for the delay getting back to you, I should be able to add the csvs as requested this week, cheers