Fix sending attachments less than 3MB

[mrashed-dev]

Description

We were not encoding the attachments properly for attachments less than 3MB. They should be b64 encoded. Now it should handle it correctly.

License

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[kraju3]

@mrashed-dev Thanks for raising this PR. I have an edge case:

What if the clients doesn't specify a file but instead specify the base64 encoded content (i.e If they are not using our utility function)

[atejada]

All good 👍

[mrashed-dev]

@kraju3 we have specified already in all the sending functions that it must be a file pointer:

# @param request_body [Hash] The values to create the message with.
    #   If you're attaching files, you must pass an array of [File] objects, or
    #   you can use {FileUtils::attach_file_request_builder} to build each object attach.

However, we can expand this function to be more flexible where we can accept a b64 encoded string, but only for attachments that total less than 3MB. Otherwise it has to be a file object because of how we stream files to the API.

[mrashed-dev]

@kraju3 function comments updated along with code to support this operation:

# @param request_body [Hash] The values to create the message with.
    #   If you're attaching files, you must pass an array of [File] objects, or
    #   you can pass in base64 encoded strings if the total attachment size is less than 3mb.
    #   You can also use {FileUtils::attach_file_request_builder} to build each object attach.