[Bug]: update_gateway does not persist passthrough_headers field

[arjavdongaonkar]

🐞 Bug Summary

Edit Gateway API does not persist the passthrough_headers field from GatewayUpdate.
Although the field exists in the GatewayUpdate model, it is ignored during update and never stored in the DB.

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🧩 Affected Component

Select the area of the project impacted:

• mcpgateway - API
• mcpgateway - UI (admin panel)
• mcpgateway.wrapper - stdio wrapper
• Federation or Transports
• CLI, Makefiles, or shell scripts
• Container setup (Docker/Podman/Compose)
• Other (explain below)

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🔁 Steps to Reproduce

1. Create a Gateway Server.
2. Reopen the "Edit" modal.
3. Fill in the Passthrough Headers input and hit save
4. Observe that Passthrough headers are not saved

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🤔 Expected Behavior

passthrough_headers should be updated on the gateway record.
Changes should be visible in the DB and returned in the GatewayRead response.

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📓 Logs / Error Output

Paste any relevant stack traces or logs here.
⚠️ Do not paste secrets, credentials, or tokens.

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🧠 Environment Info

You can retrieve most of this from the /version endpoint.

Key	Value
Version or commit	0.6.0
Runtime	Python 3.13.1
Platform / OS	Darwin 24.5.0 (arm64)
Container	none

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🧩 Additional Context (optional)

This was confirmed in the update_gateway method: while it updates name, url, tags, auth, etc., it never checks gateway_update.passthrough_headers.

[arjavdongaonkar]

Created this PR: #868