docs: add Attio integration setup guide (ext-399)

[devin-ai-integration]

Attio Integration Documentation

This PR adds comprehensive documentation for the Attio integration, including a detailed setup guide for creating and configuring OAuth 2.0 credentials.

Changes

• Added complete setup guide with step-by-step instructions
• Updated access requirements section
• Reformatted useful links into a table for better readability
• Added common OAuth scopes section
• Enhanced API gotchas section with important considerations

References

• Attio Developer Documentation
• Attio OAuth 2.0 Flow
• Attio Authorization Endpoint
• Attio Token Endpoint

Link to Devin run: https://app.devin.ai/sessions/94f14c04f0bf4a7bb75ab740686940de
Requested by: khaliq@nango.dev

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This PR improves the Attio integration documentation by replacing placeholder content with a comprehensive OAuth 2.0 setup guide. It includes detailed step-by-step instructions for creating and configuring an Attio integration, alongside accurate access requirements and available OAuth scopes.

Key Changes:
• Added a 7-step OAuth setup guide with clear instructions
• Updated access requirements with accurate information
• Added a Common Scopes section listing available permissions
• Improved document organization and readability

Affected Areas:
• docs-v2/integrations/all/attio.mdx

This summary was automatically generated by @propel-code-bot

[linear]

EXT-399 attio: document access requirements and setup guide.

[devin-ai-integration]

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[devin-ai-integration]

I've recorded a video demonstrating the complete setup process for Attio integration. The video shows the OAuth app creation process, including navigating the developer portal, configuring redirect URIs, and setting up necessary permissions.

[devin-ai-integration]

Closing due to inactivity for more than 7 days.

[devin-ai-integration]

I've addressed the feedback by changing the useful links from table to list format and removing the API gotchas section as requested.