Rework sources to be dbt models rather than manually created

[jaypeedevlin]

Closes #153, #190 and unblocks #175, #177

This PR replaces our manual schema generation macros with incremental models with on_schema_change configuration designed to make schema evolution more painfree.

Of note, it bumps the require-dbt-version to >= 1.2.0.

---

Additionally this removes the dependency on dbt_utils by using a combination of the new cross DB macros in core >=1.2.0 and a copy/paste of the surrogate_key macro.

[NiallRees]

This was an ARRAY type before for Snowflake which is currently leading to errors when I do:
dbt run -m dbt_artifacts

when I install this branch into a project which already is using dbt_artifacts:

10:11:48  Database Error in model sources (models/sources/sources.sql)
10:11:48    002023 (22000): SQL compilation error:
10:11:48    Expression type does not match column data type, expecting ARRAY but got OBJECT for column FRESHNESS
10:11:48    compiled SQL at target/run/dbt_artifacts/models/sources/sources.sql`

[jaypeedevlin]

Hmm, this will be tricky to solve in a way that's compatible to both Snowflake and Bigquery I think, given that one uses JSON and the other ARRAY

dbt_artifacts/macros/create_sources_table_if_not_exists.sql

Lines 36 to 66 in 9146d71

	{% macro snowflake__get_create_sources_table_if_not_exists_statement(database_name, schema_name, table_name) -%}
	create table {{database_name}}.{{schema_name}}.{{table_name}} (
	command_invocation_id STRING,
	node_id STRING,
	run_started_at TIMESTAMP_TZ,
	database STRING,
	schema STRING,
	source_name STRING,
	loader STRING,
	name STRING,
	identifier STRING,
	loaded_at_field STRING,
	freshness ARRAY
	)
	{%- endmacro %}
	{% macro bigquery__get_create_sources_table_if_not_exists_statement(database_name, schema_name, table_name) -%}
	create table {{database_name}}.{{schema_name}}.{{table_name}} (
	command_invocation_id STRING,
	node_id STRING,
	run_started_at TIMESTAMP,
	database STRING,
	schema STRING,
	source_name STRING,
	loader STRING,
	name STRING,
	identifier STRING,
	loaded_at_field STRING,
	freshness JSON
	)
	{%- endmacro %}

One option would be to create a specific type helper for just this column, but that seems a bit suboptimal IMO. Do you have any ideas @NiallRees?

[jaypeedevlin]

Maybe we could offer a one-time migration macro for the source tables and cut a new major version with this new method?

[NiallRees]

Think I'd be inclined to use a specific type helper (just doing an if snowflake else in the model vs a macro) rather than adding more complexity to the migration process.

[jaypeedevlin]

@NiallRees done and ready for another test.

[NiallRees]

Tested successfully on Snowflake, BigQuery and Databricks when tables already existed.