[Validator] Update NotBlank and Length validators pages with the new trimming options

- Add "trim" option to the NotBlank page
- Add "ltrim", "rtrim" and "mergeConsecutiveWhitespaces" options to the Length page

Author: renan-taranto

reference/constraints/Length.rst

@@ -133,6 +133,30 @@ max
 This required option is the "max" length value. Validation will fail if
 the given value's length is **greater** than this max value.
 
+ltrim
+~~~~~
+
+**type**: ``boolean``  **default**: ``null``
+
+If ``true``, every kind of whitespace from the **beginning** of the given value
+will be ignored while checking for its length.
+
+rtrim
+~~~~~
+
+**type**: ``boolean``  **default**: ``null``
+
+If ``true``, every kind of whitespace from the **end** of the given value will
+be ignored while checking for its length.
+
+mergeConsecutiveWhitespaces
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+**type**: ``boolean``  **default**: ``null``
+
+If ``true``, consecutive whitespaces will count as a single character while
+checking for the given value's length.
+
 charset
 ~~~~~~~
 

reference/constraints/NotBlank.rst

@@ -94,4 +94,12 @@ message
 
 This is the message that will be shown if the value is blank.
 
+trim
+~~~~
+
+**type**: ``boolean`` **default**: ``null``
+
+If ``true`` and if the given value is a ``string``, every kind of whitespace will be
+ignored while checking if it is not blank.
+
 .. include:: /reference/constraints/_payload-option.rst.inc