PUT calendar_object: Allow omission of timezones as in RFC7809

crates/ical/src/address_object.rs

@@ -17,7 +17,7 @@ use caldata::{
 };
 use chrono::{NaiveDate, Utc};
 use sha2::{Digest, Sha256};
-use std::collections::HashMap;
+use std::collections::BTreeMap;
 use std::str::FromStr;
 
 #[derive(Debug, Clone)]
@@ -134,7 +134,7 @@ impl AddressObject {
                     .into(),
                 ],
                 inner: Some(CalendarInnerDataBuilder::Event(vec![event])),
-                vtimezones: HashMap::default(),
+                vtimezones: BTreeMap::default(),
             }
             .build(None)?
             .into(),