Simple changes to the docs.
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## Summary by CodeRabbit
* **Documentation**
* Enhanced SAML SSO attribute mapping guide with support for
multi-valued arrays, default values for missing attributes, and multiple
alternative attribute name lookup.
* Clarified identity data storage location and expanded configuration
examples with resulting JWT claims and database representations.
<sub>✏️ Tip: You can customize this high-level summary in your review
settings.</sub>
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Co-authored-by: Chris Chinchilla <chris.ward@supabase.io>
