In reality you wouldn't need this for use with pywidevine, but a lot have asked me for this feature so they can use WVDs in other ways or with other software that does not support WVDs.
A by product of this change is dropped support for providing a PSSH or init data directly in any form, that includes base64.
You must now provide it as a PSSH object, e.g., `cdm.get_license_challenge(session_id, PSSH("AAAAW3Bzc2...CSEQyAA=="))`
The idea behind this is to simplify the amount of places where parsing of PSSH and Init Data to a minimal amount. The codebase is getting quite annoying with the constant jumps and places where it needs to test for base64 strings, hex strings, bytes, and direct parsed PSSH boxes or WidevinePsshData. That's a ridiculous amount of code just to take in a pssh/init data, especially when the full pssh box will eventually be discarded/unused by the Cdm, as it just cares about the init data.
Client code should pass any PSSH value they get into a PSSH object appropriately, and then store it as such, instead of as a string or bytes. This makes it overall more powerful thanks to the ability to also access the underlying PSSH data more easily with this change.
It also helps to increase contrast between a compliant Widevine Cenc Header or PSSH Box, and arbitrary data (e.g., Netflix WidevineExchange's init data) because of how you initialize the PSSH.
It also allows the user to more accurately trace the underlying final parse of the PSSH value, instead of looking at it being pinged between multiple functions.
RemoteCdm now also sends the PSSH/init_data in full box form now, the serve API will be able to handle both scenarios but in edge cases providing the full box may be the difference between a working License Request and not.
This is so you can construct a Cdm object without using `.wvd` files (nor the Device class). It also improves enforcement of some required data from the Device. The underlying Device object is discarded for it's data as it won't be required.
Note that the Client ID and Private Key related variables are now stored as private `__var` variables to further amplify their private nature and to really discourage manual read write. This is not impossible to workaround in Python but further discourages manual read/writes to the variable that could cause serious issues.
The RSA Key is also no longer stored as-is. It is now stored as PSS and PKCS1_OAEP objects, as they will be used like so. This makes it even more annoying to directly read/write the RSA key (but not impossible).
Also now more effectively migrates using the v1 Structure data.
Also fixes the migration error of possibly leaving behind VMP data. Will warn you if VMP data is already in the Client ID (if its different).
It even adds VMP data to the Client ID blob directly (instead of storing possibly duplicated). It will warn you if the Client ID already had VMP data there.
The filename is generated from client id information and has a crc32 checksum to help avoid with conflicts.
The output directory is the current working directory. You can set the directory with -o/--output.
