fix(connector): [Trustpay] fix deserialization error for incoming webhook response for trustpay and add error code mapping '800.100.203'

[prasunna09]

Type of Change

• Bugfix
• New feature
• Enhancement
• Refactoring
• Dependency updates
• Documentation
• CI/CD

Description

• fix deserialization error for incoming webhook response for trustpay
  made Code as optional field
• add error code mapping '800.100.203'

PR raised against main - #4199

Additional Changes

• This PR modifies the API contract
• This PR modifies the database schema
• This PR modifies application configuration/environment variables

Motivation and Context

How did you test it?

No testing can be done since it matches error code in production which cant be replicated

Checklist

• I formatted the code cargo +nightly fmt --all
• I addressed lints thrown by cargo clippy
• I reviewed the submitted code
• I added unit tests for my changes where possible
• I added a CHANGELOG entry if applicable