Add docs for ActiveSupport::EncryptedFile#read [ci-skip]

[whyinzoo]

Summary

Adding docs to ActiveSupport::EncryptedFile#read

Other Information

Found this on https://www.codetriage.com/

[jonathanhefner]

Suggested change

	# Read and return decrypted content
	# Reads the file and returns the decrypted content.

[jonathanhefner]

This method can raise other errors as well. For example, if raise_if_missing_key is true and the key is missing then the key.nil? call will raise MissingKeyError. Plus any errors due to an incorrect key or wrong file contents.

Also, we can link MissingContentError to its own API documentation by omitting <tt>.

[whyinzoo]

Thanks for pointing that out. I'll add that and any additional errors I see in EncryptedFile to the documentation.
I also noticed that decrypt can raise ActiveSupport::MessageEncryptor::InvalidMessage, is it customary to also include that as part of documentation? Thanks.

[jonathanhefner]

Yes, let's include ActiveSupport::MessageEncryptor::InvalidMessage too.

[jonathanhefner]

read does not raise InvalidKeyLengthError. (write / encrypt does.)

Suggested change

# - InvalidKeyLengthError if key length is invalid.

[jonathanhefner]

MissingContentError is primarily for when the encrypted file is missing, though it will be raised if the key is missing and a MissingKeyError has not already been raised. Therefore, let's put these in chronological order:

Suggested change

	# - MissingContentError if unable to decrypt content.
	# - MissingKeyError if key is missing and <tt>raise_if_missing_key</tt> is true.
	# - MissingKeyError if the key is missing and +raise_if_missing_key+ is true.
	# - MissingContentError if the encrypted file does not exist or otherwise if the key is missing.

[jonathanhefner]

Thank you, @whyinzoo! 🎉

(Backported to 7-0-stable.)