Make file config optional.

Author: CTMBNara

src/main/java/org/prebid/server/settings/FileApplicationSettings.java

@@ -77,7 +77,9 @@ public FileApplicationSettings(FileSystem fileSystem,
 
         storedIdToRequest = readStoredData(fileSystem, Objects.requireNonNull(storedRequestsDir));
         storedIdToImp = readStoredData(fileSystem, Objects.requireNonNull(storedImpsDir));
-        profileIdToProfile = readProfiles(fileSystem, Objects.requireNonNull(profilesDir), jacksonMapper);
+        profileIdToProfile = profilesDir != null // TODO: require in PBS 4.0
+                ? readProfiles(fileSystem, Objects.requireNonNull(profilesDir), jacksonMapper)
+                : Collections.emptyMap();
         storedIdToSeatBid = readStoredData(fileSystem, Objects.requireNonNull(storedResponsesDir));
         fileToCategories = readCategories(fileSystem, Objects.requireNonNull(categoriesDir), jacksonMapper);
     }

src/main/java/org/prebid/server/spring/config/SettingsConfiguration.java

@@ -77,7 +77,7 @@ FileApplicationSettings fileApplicationSettings(
                 @Value("${settings.filesystem.settings-filename}") String settingsFileName,
                 @Value("${settings.filesystem.stored-requests-dir}") String storedRequestsDir,
                 @Value("${settings.filesystem.stored-imps-dir}") String storedImpsDir,
-                @Value("${settings.filesystem.profiles-dir}") String profilesDir,
+                @Value("${settings.filesystem.profiles-dir:#{null}}") String profilesDir,
                 @Value("${settings.filesystem.stored-responses-dir}") String storedResponsesDir,
                 @Value("${settings.filesystem.categories-dir}") String categoriesDir,
                 FileSystem fileSystem,