Add PS256 encoding and decoding usage (#992)

Author: peter279k

docs/usage.rst

@@ -49,6 +49,22 @@ If you are repeatedly encoding with the same private key, reusing the same
 ``RSAPrivateKey`` also has performance benefits because it avoids the
 CPU-intensive ``RSA_check_key`` primality test.
 
+Encoding & Decoding Tokens with PS256 (RSA)
+-------------------------------------------
+
+RSA encoding and decoding require the ``cryptography`` module. See :ref:`installation_cryptography`.
+
+.. code-block:: pycon
+
+    >>> import jwt
+    >>> private_key = "-----BEGIN RSA PRIVATE KEY-----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\nKQD/JzHwNQN5+o+hy0lJavTw9NwAAb1ZzTgvq6fPwEG0b9hn0SI=\n-----END RSA PRIVATE KEY-----\n"
+    >>> public_key = "-----BEGIN PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAuNhCS6bodtd+PvKqNj+t\nYZYqTNMDkf0rcptgHhecSsMP9Vay+6NvJk1tC+IajPaE4yRJVY4jFqEt3A0MJ9sK\ne5mWDYFmzW/L6VzQvQ+0nrMc1YTEDpOf7BQhlW5W0mDj5SwSR50Lxg/acb+SMWq6\nzmhuAoLRapH17K2RWONA2vr2froxJ6N9TGtrQHygDb0p9D6jPnXEe4y+zBuj6o0b\nCkJgCVNM+CU19xBepj5caetYV28/49yl5XPi93n1ATU+7aGAKxuvjudODuHhF/Us\nZScMFSHeZW367eQldTB2w9uoIIzWO46tKimr21zYifMimjwnBQ/PLDqc7HqY0Y/r\nLQIDAQAB\n-----END PUBLIC KEY-----\n"
+    >>> encoded = jwt.encode({"some": "payload"}, private_key, algorithm="PS256")
+    >>> print(encoded)
+    eyJhbGciOiJQUzI1NiIsInR5cCI6IkpXVCJ9.eyJzb21lIjoicGF5bG9hZCJ9.s0cBw3PYkVp1H1Bh1tyYkghhGdR02TazHF1iyLlK8XZXy1A9Oy_4LJduzt7MggAsiqU4S4OmeiApgs0bLvv_cZiATVVfuqiWKaCzkIEYP9J2eDUhohEwy4i-lI3EpvlmoD_Kcxgzhcwv2pjxGGNNTdDDqr4AvYLOENd-UltUMI9YkVROTM6zPIvaBXZ1Kix3BOCSLOU8fZU8Z9PT8KTsNQYCvs-9ZKml1sr-yQtNvt6YlSqaq0w6TYRUMkClEs3rdz5QrKrdcXYM00ksAi5gWwzyI5ITMkq3HgI3fF7ytsSoLxJTUHkPeZM0PwJ1DvNLAGg5y36jk697tLA--1g09w
+    >>> jwt.decode(encoded, public_key, algorithms=["PS256"])
+    {'some': 'payload'}
+
 Specifying Additional Headers
 -----------------------------