fix: channel_id should be hyphenated

[pjenvey]

see remove_channel: it renders channel_id w/ Uuid::to_string (or via as_hyphenated in the old rust state machine db impl)

or autopush python's normalize_id: str(<uuid.UUID>)

SYNC-3444

[pjenvey]

This might also be worth doing:

diff --git a/autopush-common/src/db/dynamodb/mod.rs b/autopush-common/src/db/dynamodb/mod.rs
index 060efd9..9c52b6a 100644
--- a/autopush-common/src/db/dynamodb/mod.rs
+++ b/autopush-common/src/db/dynamodb/mod.rs
@@ -268,7 +268,7 @@ impl DbClient for DdbClientImpl {
             },
             update_expression: Some("ADD chids :channel_id SET expiry = :expiry".to_string()),
             expression_attribute_values: Some(hashmap! {
-                ":channel_id".to_string() => val!(SS => Some(channel_id)),
+                ":channel_id".to_string() => val!(SS => Some(channel_id.as_hyphenated())),
                 ":expiry".to_string() => val!(N => sec_since_epoch() + MAX_CHANNEL_TTL)
             }),
             ..Default::default()
@@ -361,7 +361,7 @@ impl DbClient for DdbClientImpl {
             },
             update_expression: Some("DELETE chids :channel_id SET expiry = :expiry".to_string()),
             expression_attribute_values: Some(hashmap! {
-                ":channel_id".to_string() => val!(SS => Some(channel_id)),
+                ":channel_id".to_string() => val!(SS => Some(channel_id.as_hyphenated())),
                 ":expiry".to_string() => val!(N => sec_since_epoch() + MAX_CHANNEL_TTL)
             }),
             return_values: Some("UPDATED_OLD".to_string()),

[jrconlin]

I wonder if we should just make a function that is "export_channel_id" or something that we always use whenever we are sending out a channel_id. Mostly just to encapsulate changes like .as_hyphenated() => .hyphenated() (or all the nonsense with base64 changes)