feat(config): Allow loading extra config from file

SoObjects/SOGo/SOGoSystemDefaults.m

@@ -25,6 +25,7 @@
 #import <Foundation/NSFileManager.h>
 #import <Foundation/NSFileManager.h>
 #import <Foundation/NSUserDefaults.h>
+#import <Foundation/NSProcessInfo.h>
 
 #import <NGExtensions/NSObject+Logs.h>
 
@@ -143,7 +144,7 @@ + (void) prepareUserDefaults
   NSBundle *bundle;
   NSString *confFiles[] = {@"/etc/sogo/debconf.conf",
                            @"/etc/sogo/sogo.conf"};
-  NSString *filename, *redirectURL;
+  NSString *filename, *redirectURL, *envFile;
   NSUInteger count;
 
   logger = [SOGoStartupLogger sharedLogger];
@@ -163,6 +164,12 @@ + (void) prepareUserDefaults
   for (count = 0; count < sizeof(confFiles)/sizeof(confFiles[0]); count++)
     _injectConfigurationFromFile (configFromFiles, confFiles[count], logger);
 
+  /* Fill/Override configuration with configuration stored in the extra
+   *  config file */
+  envFile = [[[NSProcessInfo processInfo] environment] objectForKey:@"SOGO_EXTRA_CONFIG_FILE"];
+  if (envFile)
+    _injectConfigurationFromFile (configFromFiles, envFile, logger);
+
   /* This dance is required to let other appplications (sogo-tool) use
    * options from the sogod domain while preserving the order of precedence
    *  - remove the 'sogod' domain from the user defaults search list