Simple Encryption Class: Encode a text string by replacing its characters

This class can encode a text string by replacing its characters.

It takes a given text string and generates an encoded version of characters by looking up in an array that contains replacement characters and returns the encoded string.

The class can also do the opposite, i.e. decode a previously encoded string and return the original string after being decoded using a process that is the inverse of the encoding process.

For serial number
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