Break util.cr into multiple files

src/util/validation.cr

@@ -0,0 +1,31 @@
+def validate_username(username)
+  if username.size < 3
+    raise "Username should contain at least 3 characters"
+  end
+  if (username =~ /^[A-Za-z0-9_]+$/).nil?
+    raise "Username should contain alphanumeric characters " \
+          "and underscores only"
+  end
+end
+
+def validate_password(password)
+  if password.size < 6
+    raise "Password should contain at least 6 characters"
+  end
+  if (password =~ /^[[:ascii:]]+$/).nil?
+    raise "password should contain ASCII characters only"
+  end
+end
+
+def validate_archive(path : String) : Exception?
+  file = nil
+  begin
+    file = ArchiveFile.new path
+    file.check
+    file.close
+    return
+  rescue e
+    file.close unless file.nil?
+    e
+  end
+end