Increases read timeout for Service Desk custom email verification

What does this MR do and why?

Contributes Custom Email: Rescue Net::ReadTimeout and incre... (#430209 - closed)

Feature issue Configurable e-mail address for service desk (#329990 - closed)

Increases read timeout for Service Desk custom email verification

When providing an incorrect configuration some SMTP servers respond slowly. That disguises the real configuration issue. In tests with Microsoft 365 7 instead of 5 worked fine and raised the correct error (so the server was able to respond).

We will only use the increased timeout for the Service Desk custom email verification email. All other settings remain unchanged. Also sending Service Desk emails using custom email settings will use the default read timeout.

There will be two follow-up MRs:

1. Also rescue Net::ReadTimeout in ServiceDesk::CustomEmailVerifications::CreateService (#431597 (closed))
2. Rescue Net::SMTPAuthenticationError in ServiceDesk::CustomEmailVerifications::CreateService(#429929 (closed)`

Screenshots or screen recordings

🚫 backend only

How to set up and validate locally

Ping me, if you'd like to have detailed validation steps 🙂 👍

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.