Add Display impl for DateTime (#3235)

## Motivation and Context
<!--- Why is this change required? What problem does it solve? -->
It implements Display trait For DateTime

<!--- If it fixes an open issue, please link to the issue here -->
#3161

## Description
<!--- Describe your changes in detail -->
I implemented Display trait for DateTime

## Testing
<!--- Please describe in detail how you tested your changes -->
<!--- Include details of your testing environment, and the tests you ran
to -->

I used this test
```rust
    fn test_display_formatting() {
        // Create a DateTime instance for testing
        let datetime = DateTime {
            seconds: 1636761600, // Example timestamp (replace with your actual timestamp)
            subsecond_nanos: 123456789, // Example subsecond nanos (replace with your actual value)
        };

        // Expected RFC-3339 formatted string
        let expected = "2021-11-13T00:00:00.123456789Z";

        // Format the DateTime using Display trait
        let formatted = format!("{}", datetime);

        // Assert that the formatted string matches the expected result
        assert_eq!(formatted, expected);
    }
```

<!--- see how your change affects other areas of the code, etc. -->

## Checklist
<!--- If a checkbox below is not applicable, then please DELETE it
rather than leaving it unchecked -->
- [ ] I have updated `CHANGELOG.next.toml` if I made changes to the
smithy-rs codegen or runtime crates
- [ ] I have updated `CHANGELOG.next.toml` if I made changes to the AWS
SDK, generated SDK code, or SDK runtime crates

----

_By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice._

---------

Co-authored-by: Hakan Vardar <[email protected]>

CHANGELOG.next.toml

@@ -92,3 +92,15 @@ the [deprecations removal list](https://github.com/smithy-lang/smithy-rs/discuss
 references = ["smithy-rs#3222"]
 meta = { "breaking" = true, "tada" = false, "bug" = false }
 author = "jdisanti"
+
+[[aws-sdk-rust]]
+message = "Add `Display` impl for `DateTime`."
+references = ["smithy-rs#3183"]
+meta = { "breaking" = false, "tada" = true, "bug" = false }
+author = "HakanVardarr"
+
+[[smithy-rs]]
+message = "Add `Display` impl for `DateTime`."
+references = ["smithy-rs#3183"]
+meta = { "breaking" = false, "tada" = true, "bug" = false, "target" = "all" }
+author = "HakanVardarr"

rust-runtime/aws-smithy-types/Cargo.toml

@@ -14,7 +14,15 @@ repository = "https://github.com/smithy-lang/smithy-rs"
 byte-stream-poll-next = []
 http-body-0-4-x = ["dep:http-body-0-4"]
 hyper-0-14-x = ["dep:hyper-0-14"]
-rt-tokio = ["dep:http-body-0-4", "dep:tokio-util", "dep:tokio", "tokio?/rt", "tokio?/fs", "tokio?/io-util", "tokio-util?/io"]
+rt-tokio = [
+    "dep:http-body-0-4",
+    "dep:tokio-util",
+    "dep:tokio",
+    "tokio?/rt",
+    "tokio?/fs",
+    "tokio?/io-util",
+    "tokio-util?/io",
+]
 test-util = []
 serde-serialize = []
 serde-deserialize = []

rust-runtime/aws-smithy-types/src/date_time/mod.rs

@@ -13,6 +13,7 @@ use std::cmp::Ordering;
 use std::convert::TryFrom;
 use std::error::Error as StdError;
 use std::fmt;
+use std::fmt::Display;
 use std::time::Duration;
 use std::time::SystemTime;
 use std::time::UNIX_EPOCH;
@@ -329,6 +330,12 @@ impl Ord for DateTime {
     }
 }
 
+impl Display for DateTime {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let date = self.fmt(Format::DateTime).map_err(|_| fmt::Error)?;
+        write!(f, "{}", date)
+    }
+}
 /// Failure to convert a `DateTime` to or from another type.
 #[derive(Debug)]
 #[non_exhaustive]
@@ -372,6 +379,21 @@ mod test {
     use time::format_description::well_known::Rfc3339;
     use time::OffsetDateTime;
 
+    #[test]
+    fn test_display_date_time() {
+        let date_time = DateTime::from_secs(1576540098);
+        assert_eq!(format!("{}", date_time), "2019-12-16T23:48:18Z");
+
+        let date_time = DateTime::from_fractional_secs(1576540098, 0.52);
+        assert_eq!(format!("{}", date_time), "2019-12-16T23:48:18.52Z");
+
+        let date_time = DateTime::from_secs(1699942527);
+        assert_eq!(format!("{}", date_time), "2023-11-14T06:15:27Z");
+
+        let date_time = DateTime::from_secs(16995123);
+        assert_eq!(format!("{}", date_time), "1970-07-16T16:52:03Z");
+    }
+
     #[test]
     fn test_fmt() {
         let date_time = DateTime::from_secs(1576540098);