treewide: use boolToString function

nixos/modules/services/databases/cassandra.nix

@@ -21,8 +21,8 @@ let
   cassandraConf = ''
     cluster_name: ${cfg.clusterName}
     num_tokens: 256
-    auto_bootstrap: ${if cfg.autoBootstrap then "true" else "false"}
-    hinted_handoff_enabled: ${if cfg.hintedHandOff then "true" else "false"}
+    auto_bootstrap: ${boolToString cfg.autoBootstrap}
+    hinted_handoff_enabled: ${boolToString cfg.hintedHandOff}
     hinted_handoff_throttle_in_kb: ${builtins.toString cfg.hintedHandOffThrottle}
     max_hints_delivery_threads: 2
     max_hint_window_in_ms: 10800000 # 3 hours
@@ -62,7 +62,7 @@ let
     rpc_keepalive: true
     rpc_server_type: sync
     thrift_framed_transport_size_in_mb: 15
-    incremental_backups: ${if cfg.incrementalBackups then "true" else "false"}
+    incremental_backups: ${boolToString cfg.incrementalBackups}
     snapshot_before_compaction: false
     auto_snapshot: true
     column_index_size_in_kb: 64
@@ -89,7 +89,7 @@ let
       truststore: ${cfg.trustStorePath}
       truststore_password: ${cfg.trustStorePassword}
     client_encryption_options:
-      enabled: ${if cfg.clientEncryption then "true" else "false"}
+      enabled: ${boolToString cfg.clientEncryption}
       keystore: ${cfg.keyStorePath}
       keystore_password: ${cfg.keyStorePassword}
     internode_compression: all

nixos/modules/services/databases/mongodb.nix

@@ -4,8 +4,6 @@ with lib;
 
 let
 
-  b2s = x: if x then "true" else "false";
-
   cfg = config.services.mongodb;
 
   mongodb = cfg.package;