This diff introduces changes for using the `init` and a global configuration struct from D5329.
Instead of providing a certificate, fcm key for every function call we can initialize it once the service starts.
The function and struct are introduced in D5329.
Related Linear task: [[ https://linear.app/comm/issue/ENG-1737/change-to-use-builder-approach-and-thread-local-in-rust-notification | ENG-1737 ]]