docs: add ClickUp integration setup guide (ext-393)

[devin-ai-integration]

ClickUp Integration Documentation

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

Changes

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

References

• ClickUp API Documentation
• ClickUp Authentication Documentation
• ClickUp OAuth Flow
• ClickUp OAuth Endpoints

Link to Devin run: https://app.devin.ai/sessions/94f14c04f0bf4a7bb75ab740686940de
Requested by: [email protected]

[linear]

EXT-393 clickup: 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 ClickUp 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.