Move Payload pretty-print from Display to Debug

[yuandrew]

What was changed

Spencer previously implemented a pretty-print for Display for Payload. Debug was not touched because prost automatically generated the Debug impl for Payload. Prost and tonic-build now support skipping the Debug impl, tokio-rs/prost#797, so we can leverage this to provide our own Debug impl.

Also added support to skip this truncation by specifying the TEMPORAL_PRINT_FULL_PAYLOADS env variable

Why?

A nice-to-have feature to make debug logs more readable.

Checklist

1. Closes
   [Feature Request] Pretty print Payload data #806

2. How was this tested:

Generated temporal.api.common.v1.rs now generates

#[cfg_attr(
    feature = "serde_serialize",
    derive(::serde::Serialize, ::serde::Deserialize)
)]
#[allow(clippy::derive_partial_eq_without_eq)]
#[derive(Clone, PartialEq, ::prost::Message)]
#[prost(skip_debug)]
pub struct Payload {
    #[prost(map = "string, bytes", tag = "1")]
    pub metadata: ::std::collections::HashMap<
        ::prost::alloc::string::String,
        ::prost::alloc::vec::Vec<u8>,
    >,
    #[prost(bytes = "vec", tag = "2")]
    pub data: ::prost::alloc::vec::Vec<u8>,
}

impl std::fmt::Debug for Payload {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        if self.data.len() > 64 {
            let mut windows = self.data.as_slice().windows(32);
            write!(
                f,
                "[{}..{}]",
                BASE64_STANDARD.encode(windows.next().unwrap_or_default()),
                BASE64_STANDARD.encode(windows.next_back().unwrap_or_default())
            )
        } else {
            write!(f, "[{}]", BASE64_STANDARD.encode(&self.data))
        }
    }
}

4. Any docs updates needed?

[Sushisource]

Yaaaaaaay! I'm jazzed for this.

My only remaining thought is that sometimes it may be pretty important to get the full payload dumped to the log, even if it is longer than 64 bytes. I can't really think of any reasonable way to configure than other than an environment variable.

Let's add that so we at least have the option when debugging stuff or if a customer needs to show us some info. We can call it something like TEMPORAL_PRINT_FULL_PAYLOADS and if that's set in the environment, then don't do the >64 byte truncation thing

[Sushisource]

Noice!