Remove legacy name for the database path

Summary:
Remove the legacy `db` name for the database path. This allows for specifying the database path
under `raft_database` under `wa_raft` similarly to how it should be specified per-application.

Differential Revision: D78370203

fbshipit-source-id: 9280b1d0dcda583063a80bac2c44225d612a1113

Author: hsun324

include/wa_raft.hrl

@@ -11,6 +11,11 @@
 %% Registered information about applications and partitions
 %%-------------------------------------------------------------------
 
+%% Name of the application environment key that is expected to contain a path
+%% to the directory in which RAFT should place the partition paths for the
+%% RAFT partitions under a RAFT client application. This environment value uses
+%% the application search order to determine the value to use.
+-define(RAFT_DATABASE, raft_database).
 %% Default location containing databases for RAFT partitions part of a RAFT client application
 -define(RAFT_DATABASE_PATH(Application), (wa_raft_env:database_path(Application))).
 %% Registered database location for the specified RAFT partition

src/wa_raft_env.erl

@@ -32,7 +32,7 @@
 
 -spec database_path(Scope :: scope()) -> Root :: file:filename().
 database_path(Scope) ->
-    case get_env(Scope, {raft_database, db}) of
+    case get_env(Scope, ?RAFT_DATABASE) of
         {ok, Root} -> Root;
         undefined  -> error({no_configured_database_path, Scope})
     end.