exmdb: reduce "cache_interval" default value

Reduce the sqlite idle closing time to conserve resources.
(Opening takes about 1500µs; accessing an open one is 4µs.)

Author: jengelh

doc/exmdb_provider.4gx

@@ -36,7 +36,7 @@ The usual config file location is /etc/gromox/exmdb_provider.cfg.
 \fBcache_interval\fP
 The inactivity timer after which a mailbox's sqlite files are closed.
 .br
-Default: \fI2 hours\fP
+Default: \fI15min\fP
 .br
 Lower limit: 1s
 .TP

exch/exmdb/main.cpp

@@ -43,7 +43,7 @@ static constexpr cfg_directive exmdb_gromox_cfg_defaults[] = {
 };
 
 static constexpr cfg_directive exmdb_cfg_defaults[] = {
-	{"cache_interval", "2h", CFG_TIME, "1s"},
+	{"cache_interval", "15min", CFG_TIME, "1s"},
 	{"dbg_synthesize_content", "0"},
 	{"enable_dam", "1", CFG_BOOL},
 	{"exmdb_body_autosynthesis", "1", CFG_BOOL},