Add chrono_tz scalar

Cargo.toml

@@ -14,7 +14,7 @@ categories = ["network-programming", "asynchronous"]
 readme = "README.md"
 
 [features]
-default = ["bson", "uuid", "url", "validators"]
+default = ["bson", "uuid", "url", "chrono-tz", "validators"]
 validators = ["regex", "once_cell"]
 
 [dependencies]
@@ -39,6 +39,7 @@ regex = { version = "1.3.5", optional = true }
 bson = { version = "0.14.1", optional = true }
 uuid = { version = "0.8.1", optional = true }
 url = { version = "2.1.1", optional = true }
+chrono-tz = { version = "0.5.1", optional = true }
 
 [dev-dependencies]
 async-std = { version = "1.5.0", features = ["attributes"] }

src/scalars/chrono_tz.rs

@@ -0,0 +1,22 @@
+use crate::{impl_scalar_internal, Result, Scalar, Value};
+use chrono_tz::Tz;
+use std::str::FromStr;
+
+impl Scalar for Tz {
+    fn type_name() -> &'static str {
+        "TimeZone"
+    }
+
+    fn parse(value: &Value) -> Option<Self> {
+        match value {
+            Value::String(s) => Some(Tz::from_str(&s).ok()?),
+            _ => None,
+        }
+    }
+
+    fn to_json(&self) -> Result<serde_json::Value> {
+        Ok(Tz::name(self).into())
+    }
+}
+
+impl_scalar_internal!(Tz);

src/scalars/mod.rs

@@ -1,4 +1,5 @@
 mod bool;
+mod chrono_tz;
 mod datetime;
 mod floats;
 mod id;