fix(self-hosted): allow larger OAuth response headers in Docker guide

[chimit]

The Docker deployment guide now includes Nginx buffer settings that allow larger OAuth response headers. This prevents a 502 on the Google sign-in callback when Nginx reports upstream sent too big header while reading response header from upstream.

How to reproduce

Deploy Chatwoot with Docker Compose and the guide's Nginx example, configure Google sign-in, and follow /omniauth/google_oauth2/callback with a response header block larger than Nginx's default 4–8 KiB proxy buffer.

What changed

Increase proxy_buffer_size to 32 KiB and set proxy_buffers high enough to satisfy Nginx's buffer-size checks, including on systems with 4 KiB memory pages. The configuration was syntax-checked with proxy_buffering off, as shown in the guide.

Related Nginx sample config PR: chatwoot/chatwoot#16083

[Copilot]

Copilot review overview

🟡 Changes recommended

Two of the three added directives (proxy_buffers and proxy_busy_buffers_size) have no effect while proxy_buffering off; is set, so the documented config is potentially misleading about what fixes the issue.

Review effort: Balanced
Findings: 1

Open (1)

• Remove ineffective proxy buffer directives when buffering is off · New

What changed in this PR

This PR updates the self-hosted Docker deployment guide (self-hosted/deployment/docker.mdx) to add Nginx proxy buffer settings inside the reverse-proxy location / block. The goal is to prevent a 502 error on the Google sign-in callback caused by Nginx reporting upstream sent too big header while reading response header from upstream, which happens when OAuth response headers (e.g., large session cookies) exceed the default 4–8 KiB proxy buffer.

Changes:

• Adds proxy_buffer_size 32k; to allow reading larger OAuth response headers.
• Adds proxy_buffers 8 16k; and proxy_busy_buffers_size 32k; as compatible companion values.
• Adds an explanatory comment describing the intent of the buffer settings.

File	Description
self-hosted/​deployment/​docker.mdx	Adds Nginx proxy buffer directives to the documented reverse-proxy config to avoid a 502 on the OAuth callback from oversized response headers.

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