Info about MFA (#6380)

## What are you changing in this pull request and why?

See: https://dbt-labs.slack.com/archives/C05CJT5MJF2/p1729019209832589

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<!-- vercel-deployment-preview -->
---
🚀 Deployment available! Here are the direct links to the updated files:


-
https://docs-getdbt-com-git-mfa-dbt-labs.vercel.app/docs/cloud/manage-access/mfa
-
https://docs-getdbt-com-git-mfa-dbt-labs.vercel.app/docs/dbt-versions/release-notes

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website/docs/docs/cloud/manage-access/mfa.md

@@ -7,6 +7,13 @@ sidebar: null
 
 # Multi-factor authentication
 
+:::important
+
+
+dbt Cloud enforces multi-factor authentication (MFA) for all users with username and password credentials. If MFA is not set up, you will see a notification bar prompting you to configure one of the supported methods when you log in. If you do not, you will have to configure MFA upon subsequent logins, or you will be unable to access dbt Cloud.
+
+:::
+
 dbt Cloud provides multiple options for multi-factor authentication (MFA). MFA provides an additional layer of security to username and password logins for Developer and Team plan accounts. The available MFA methods are:
 
 - SMS verification code (US-based phone numbers only)

website/docs/docs/dbt-versions/release-notes.md

@@ -19,7 +19,8 @@ Release notes are grouped by month for both multi-tenant and virtual private clo
 \* The official release date for this new format of release notes is May 15th, 2024. Historical release notes for prior dates may not reflect all available features released earlier this year or their tenancy availability.
 
 ## October 2024
-
+
+- **Behavior change:** [Multi-factor authentication](/docs/cloud/manage-access/mfa) is now enforced on all users who log in with username and password credentials. 
 - **Enhancement**: The dbt Semantic Layer JDBC now allows users to paginate `semantic_layer.metrics()` and `semantic_layer.dimensions()` for metrics and dimensions using `page_size` and `page_number` parameters. Refer to [Paginate metadata calls](/docs/dbt-cloud-apis/sl-jdbc#querying-the-api-for-metric-metadata) for more information.
 - **Enhancement**: The dbt Semantic Layer JDBC now allows you to filter your metrics to include only those that contain a specific substring, using the `search` parameter. If no substring is provided, the query returns all metrics. Refer to [Fetch metrics by substring search](/docs/dbt-cloud-apis/sl-jdbc#querying-the-api-for-metric-metadata) for more information.
 - **Fix**: The [dbt Semantic Layer Excel integration](/docs/cloud-integrations/semantic-layer/excel) now correctly surfaces errors when a query fails to execute. Previously, it was not clear why a query failed to run.