Escape control-characters in generated swagger

When some table's description has `control-characters`, likes
`\t` `\n`,
swagger that generated by `/api.php` is a defective json

Add test for filter in condition with strings

Add test for filter in condition with strings

in seems to work with strings as well

That seems to work fine, so I thought I might as well add a test and document it in the README.

Add Python php_crud_api_transform.py to README

Transform algorithm in python 3

added tests for tenancy + fix for PHP 7.2

Fix typo

Use utf8mb4 instead of utf8 in commented-out starter code

'utf8' in mySQL is actually a 3-byte encoding that cannot encode characters that occupy 4 bytes in UTF-8. 'utf8mb4' is a saner default.

Use PHPUnit\Framework\TestCase instead of PHPUnit_Framework_TestCase

Correct 400 response to malformed json in POST

Symptom:
----------
Trying to create an object sending a seemingly correct JSON request in a
POST message - was giving a 404 not found error.  When looking at the cause
in the browser devtools - the body of the response contained "Not found (input)"

Cause:
-------
We were trying to validate parameters - even when the POST body
contained invalid JSON.  We call json_decode($data) in retrieveInputs
The JSON request was malformed and it had omitted the double quotes.
example: { fieldName : "fieldValue" }

Expected behavior and fix:
---------------------------
A POST request with malformed JSON should get a 400 "bad request"
response. Even more helpful would be an error code indicating why the
JSON was bad.

If we call json_decode(), afterwards, we immediately call
json_last_error(), and if the return value does not match
JSON_ERROR_NONE, we send it across bundled in a 400 response, so that
the user may rectify the cause by looking at the exact error message.

The possible error messages right now are:

    CODE  CONSTANT-ERROR MESSAGE

    0     JSON_ERROR_NONE-No error has occurred
    1     JSON_ERROR_DEPTH-The maximum stack depth has been exceeded
    2     JSON_ERROR_STATE_MISMATCH-Invalid or malformed JSON
    3     JSON_ERROR_CTRL_CHAR-Control character error, possibly incorrectly encoded
    4     JSON_ERROR_SYNTAX-Syntax error
    5     JSON_ERROR_UTF8-Malformed UTF-8 characters, possibly incorrectly encoded
    6     JSON_ERROR_RECURSION-One or more recursive references in the value to be encoded
    7     JSON_ERROR_INF_OR_NAN-One or more NAN or INF values in the value to be encoded
    8     JSON_ERROR_UNSUPPORTED_TYPE-A value of a type that cannot be encoded was given
    9     JSON_ERROR_INVALID_PROPERTY_NAME-A property name that cannot be encoded was given
    10    JSON_ERROR_UTF16-Malformed UTF-16 characters, possibly incorrectly encoded

After the fix:
-------------
On malformed JSON in the POST body - the following is returned:
    The request could not be understood by the server due to malformed
    syntax. The client SHOULD NOT repeat the request without modifications.
    (Error decoding input JSON. json_last_error code: 4)

If REQUEST_METHOD is not set - we throw an exception that says something
like:
    'Bad request (Error decoding input JSON. json_last_error code: 4)'

In order to accommodate this change in behavior - in the test suite, we
need a new method expectPattern (as the error code in the end of the
string may change, but the starting pattern stays the same - (/^Bad
request.*$/)

Add a parameter expected by mysqli_error()

Handle leading whitespace in JSON body

Issue:
When sending JSON in the body of a POST
request from an HTML form - for creating
a new record, a new record was being created,
but with null as the value for all the fields,
instead of the values supplied.

Cause:
The template text in the textarea field, in the
HTML form had some leading whitespace. On looking
through the source, json_decode is being called
only if the first character of the $data variable
is a '{' or a '['.

JSON Specification RFC4627
https://tools.ietf.org/html/rfc4627#section-2

says that insignificant
whitespace is allowed before or after any of the
six structural characters - '{','[',']','}',':',','

where whitespace is defined as:
ws = *(
                %x20 /              ; Space
                %x09 /              ; Horizontal tab
                %x0A /              ; Line feed or New line
                %x0D                ; Carriage return
            )

Fix:
trim the above characters from the beginning and ending
of the received data before checking that the first
character is a '[' or '{'

Update api.php to fix API documentation

Updated the Delete command in the core.php file