feat(events): Add events framework for registering events

[lsampras]

Type of Change

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

Description

• Add a separate events crate for the events framework & implementation
• Add a request State that will handle the request scoped state
• This state can be mutable & is scoped to a particular request only
• Generate this state as part of server_wrap that can be used to collect the request metadata & mutable variables to be used

Additional Changes

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

Motivation and Context

• Adding events framework would need a request scoped context
• In order to satisfy all such requirements of passing around a mutable state/variables we've added the RequestState that would be valid for the duration for a request
• Since this State represents the request variables pertaining to the request such as flow / request id / trace id / connector etc can be easily recorded along with other domain variables

How did you test it?

• Since this PR doesn't involve any new functionality I just ran the postman tests with stripe to verify this

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

[Chethan-rao]

Routing specific changes looks fine