Fix | V1 Encoded Files In Fixtures

[Sammyjo20]

There was an issue which was raised in discussion #148 where if a request returned a downloadable file, the fixture could not be recorded because it threw an exception "Malformed UTF-8 characters, possibly incorrectly encoded"

@derheyne Came up with a brilliant idea to base64_encode() the response body if it cannot detect UTF-8 encoding. This is also backwards compatible because of the added encoding option.

[what-the-diff]

• Added a new test to check that the file data is recorded correctly.
• Updated FixtureData class so it can handle binary files and encode them in base64 if they are not UTF-8 encoded.
• Fixed deprecation message for invalid request keys, as this was causing tests to fail on PHP 8+.

[Sammyjo20]

Self review

[Sammyjo20]

@derheyne Let me know if you're happy with this and I'll roll it out

[derheyne]

Looks good to me! Thank you so much for the fast implementation :)

Before you merge it let me quickly test it against our code base.

[derheyne]

Works perfectly in our code base!

[Sammyjo20]

Great thank you for testing!