@W-19854606: Strict Mode & Raise validation errors for missing schema and permissions

[aditya-balachander]

Snowfakery strict-mode

• Added strict-mode support to the snowfakery task in CumulusCI.
• When enabled, the Snowfakery recipe is first validated using Snowfakery’s strict-mode.
• Standard mapping validations then run as usual.
• Data loading occurs only if both validations succeed.
• If either validation fails, errors are raised and the data load does not proceed.

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Bug Fixes

What changed and why

• Missing sObject: now an error (previously warning in validate-only). The run would fail at execution time, so validation should surface it as blocking.
• sObject permission denied: now an error. Lack of createable/updateable/queryable already fails execution; validation now mirrors that.
• Missing field or field not visible: now an error when not using drop_missing. Execution would fail without the field, so validation should flag it.
• Field permission denied: now an error when not using drop_missing. Lack of required FLS blocks execution; validation should indicate that.
• Ambiguous namespaced field (both f and inject(f) exist): kept as warning. The loader explicitly chooses one and can proceed; this is informational, not blocking.

Why change warnings to errors?

• Validation-only previously gave “green” results despite conditions that would raise BulkDataException at runtime. Converting these to errors makes validation truthful and prevents false confidence.
• Users can still opt into drop_missing to auto-trim problematic fields/steps; otherwise, the validation report now matches runtime strictness.

[jkasturi-sf]

Looks good