Implement offline POST method for starting an offline participation

config/locales/en.yml

@@ -74,6 +74,8 @@ en:
         processed: Processed?
         text: Content
         time: Time
+      offline:
+        name: Your name
       puzzle:
         brand: Brand
         image: Image
@@ -112,6 +114,12 @@ en:
               blank: "No file selected"
               empty: "This file is empty"
               not_a_csv_file: "it must be a CSV file"
+        offline:
+          attributes:
+            name:
+              blank: Please enter a name for your participation
+            start_image:
+              blank: Please upload an image
         puzzle:
           attributes:
             name:
@@ -216,6 +224,7 @@ en:
       refresh: Refresh
       sign_in: Sign in
       save: Save
+      start: Click here to start your participation
     field: Field
     none: No field selected
     rank: Rank
@@ -232,6 +241,8 @@ en:
     home: My contests
     settings: Settings
     log_out: Log out
+  offlines:
+    start_image_select: Enter your photo of the puzzle with the provided code written on a paper before starting it
   puzzles:
     destroy:
       notice: Puzzle deleted