Add secondary_profiles to profile.py

[aranke]

Resolves XPLAT-241.

Problem

We need to parse secondary_profiles associated with a given profile.

Solution

• Create a new secondary_profiles dict on the Profile class.
• Validate and load each secondary profile as if they were primary profiles.
• Allow target_name to be optional iff a secondary profile has a single target.
• Add tests.

Checklist

• I have read the contributing guide and understand what's expected of me.
• I have run this code in development, and it appears to resolve the stated issue.
• This PR includes tests, or tests are not required or relevant for this PR.
• This PR has no interface changes (e.g., macros, CLI, logs, JSON artifacts, config files, adapter interface, etc.) or this PR has already received feedback and approval from Product or DX.
• This PR includes type annotations for new and modified functions.

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.96%. Comparing base (7041e58) to head (cd7472b).
Report is 7 commits behind head on main.

❌ Your patch status has failed because the patch coverage (42.85%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #11308   +/-   ##
=======================================
  Coverage   88.95%   88.96%           
=======================================
  Files         189      189           
  Lines       24169    24182   +13     
=======================================
+ Hits        21500    21513   +13     
  Misses       2669     2669           

Flag	Coverage Δ
integration	86.25% <42.85%> (-0.03%)	⬇️
unit	62.55% <100.00%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
Unit Tests	62.55% <100.00%> (+0.02%)	⬆️
Integration Tests	86.25% <42.85%> (-0.03%)	⬇️

[aranke]

Converted to draft temporarily to see if I can address feedback from @amychen1776 re making target optional for secondary profiles.

[mikealfare]

I left a few minor nits and one readability/maintainability suggestion. As far as interfaces go, this aligns with what the base adapter will expect (basically secondary_profiles).

[mikealfare]

Approved from Adapters' point of view.

[MichelleArk]

Why is this event necessary in this case?

[aranke]

The event name is slightly misleading, but the message is useful for debugging purposes to indicate that we inferred a target_name:

dbt-core/core/dbt/events/types.py

Lines 68 to 73 in e60b41d

	class MissingProfileTarget(InfoLevel):
	def code(self) -> str:
	return "A005"
	def message(self) -> str:
	return f"target not specified in profile '{self.profile_name}', using '{self.target_name}'"

I'll add a comment for the same.

[aranke]

Added a comment here, let me know if any other changes are needed here.