GUACAMOLE-857: Merge add guacamole-auth-header to Docker image

guacamole-docker/bin/start.sh

@@ -640,6 +640,18 @@ END
     ln -s /opt/guacamole/duo/guacamole-auth-*.jar   "$GUACAMOLE_EXT"
 }
 
+##
+## Adds properties to guacamole.properties which configure the header
+## authentication provider.
+##
+associate_header() {
+    # Update config file
+    set_optional_property "http-auth-header"         "$HTTP_AUTH_HEADER"
+
+    # Add required .jar files to GUACAMOLE_EXT
+    ln -s /opt/guacamole/header/guacamole-auth-*.jar "$GUACAMOLE_EXT"
+}
+
 ##
 ## Starts Guacamole under Tomcat, replacing the current process with the
 ## Tomcat process. As the current process will be replaced, this MUST be the
@@ -782,6 +794,11 @@ if [ -n "$DUO_API_HOSTNAME" ]; then
     associate_duo
 fi
 
+# Use header if specified.
+if [ "$HEADER_ENABLED" = "true" ]; then
+    associate_header
+fi
+
 # Set logback level if specified
 if [ -n "$LOGBACK_LEVEL" ]; then
     unzip -o -j /opt/guacamole/guacamole.war WEB-INF/classes/logback.xml -d $GUACAMOLE_HOME