Shorten the default retention, dramatically.

The original retention values were loosely based on Slack's retention, for lack of a more specific motivator. Today's election results have changed my views; the service now defaults to retention more in line with the needs of communities for which deep message history may be a risk:

* Unused channels expire after 7 days.
* Used channels expire when their last message expires (as before).
* Deleted channels are purged after 6 hours (which is in line with the purge behaviour of messages).
* Messages expire after 15 days.
* Deleted messages are purged after 6 hours (as before).

No changes have been made to token expiry.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/test/fixtures/mod.rs b/src/test/fixtures/mod.rs
index 470b31a..21e4483 100644
--- a/src/test/fixtures/mod.rs
+++ b/src/test/fixtures/mod.rs
@@ -24,7 +24,7 @@ pub fn now() -> RequestedAt {
 }
 
 pub fn old() -> RequestedAt {
-    let timestamp = Utc::now() - TimeDelta::days(95);
+    let timestamp = Utc::now() - TimeDelta::days(20);
     timestamp.into()
 }