Add feature-gate for ldap.

Signed-off-by: Jason Volk <jason@zemos.net>

src/service/Cargo.toml

@@ -53,6 +53,9 @@ jemalloc_stats = [
 	"tuwunel-core/jemalloc_stats",
 	"tuwunel-database/jemalloc_stats",
 ]
+ldap = [
+	"dep:ldap3",
+]
 media_thumbnail = [
 	"dep:image",
 ]
@@ -88,6 +91,7 @@ image.optional = true
 ipaddress.workspace = true
 itertools.workspace = true
 ldap3.workspace = true
+ldap3.optional = true
 log.workspace = true
 loole.workspace = true
 lru-cache.workspace = true