Messages: Filters: Implement b64 decode

[fallen-up]

Issue submitter TODO list

• I've looked up my issue in FAQ
• I've searched for an already existing issues here
• I've tried running main-labeled docker image and the issue still persists there
• I'm running a supported version of the application which is listed here

Describe the bug (actual behavior)

in the old provectus version we could use groovy script:

String body = value.body.split(/\./)[1]
String unencoded = new String(Base64.decoder.decode(body), 'UTF-8')
unencoded.contains('aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee')

after removing groovy #98 try to do this:
base64decode(record.key.body.split('.')[1]).contains('aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee')

but we get an error:

400
CEL error. Original expression: base64decode(record.key.body.split('.')[1]).contains('aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee'). Error message: ERROR: <input>:1:13: undeclared reference to 'base64decode' (in container '') | base64decode(record.key.body.split('.')[1]).contains('aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee') | ............^ ERROR: <input>:1:35: undeclared reference to 'split' (in container '') | base64decode(record.key.body.split('.')[1]).contains('aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee') | ..................................^

Expected behavior

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Your installation details

1.0

Steps to reproduce

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Additional context

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