Code clean up with declare strict and php stan level 9 checks

add "declare(strict_types=1);" to all pages

Add a json handler class to handle that json_decode always returns array<mixed> and throws error otherwise
On failure these will throw the normal JSON encoded error was FAILURE with code "J-" and the number is the json error
If 0 then the return was null or some other problem that did not return an array

amount is float and not string and checks are done that the returned value is a float

various updates for phpdoc array delcarations
- curl header is array<int, string>
- the log array is proper declared as array with string key and a list of mixed arrays

test/phpUnit/AmazonIncentivesTest.php

@@ -351,7 +351,7 @@ final class AmazonIncentivesTest extends TestCase
             // numeric number
             $this->assertIsNumeric(
                 $funds->getAmount(),
-                'Assert amoount is numerc'
+                'Assert amoount is numeric'
             );
             // USD, JPY, etc
             $this->assertIsString(