Enable RS256/ES256 and other algorithms for JWT strategy (#943)

* Implement RS256 for JWT auth

* Update docs with RS256 example

* Added ES256 tests

* Format with isort and black

* Removed example RSA key pair (so as not to tempt people to use it)

* Added pyjwt[crypto] to requirements

* Removed pycryptodome by hardcoding example keys

* Removed unnecessary Tuple import from typing

fastapi_users/authentication/strategy/jwt.py

@@ -18,10 +18,22 @@ class JWTStrategy(Strategy, Generic[models.UC, models.UD]):
         secret: SecretType,
         lifetime_seconds: Optional[int],
         token_audience: List[str] = ["fastapi-users:auth"],
+        algorithm: str = "HS256",
+        public_key: Optional[SecretType] = None,
     ):
         self.secret = secret
         self.lifetime_seconds = lifetime_seconds
         self.token_audience = token_audience
+        self.algorithm = algorithm
+        self.public_key = public_key
+
+    @property
+    def encode_key(self) -> SecretType:
+        return self.secret
+
+    @property
+    def decode_key(self) -> SecretType:
+        return self.public_key or self.secret
 
     async def read_token(
         self, token: Optional[str], user_manager: BaseUserManager[models.UC, models.UD]
@@ -30,7 +42,9 @@ class JWTStrategy(Strategy, Generic[models.UC, models.UD]):
             return None
 
         try:
-            data = decode_jwt(token, self.secret, self.token_audience)
+            data = decode_jwt(
+                token, self.decode_key, self.token_audience, algorithms=[self.algorithm]
+            )
             user_id = data.get("user_id")
             if user_id is None:
                 return None
@@ -47,7 +61,9 @@ class JWTStrategy(Strategy, Generic[models.UC, models.UD]):
 
     async def write_token(self, user: models.UD) -> str:
         data = {"user_id": str(user.id), "aud": self.token_audience}
-        return generate_jwt(data, self.secret, self.lifetime_seconds)
+        return generate_jwt(
+            data, self.encode_key, self.lifetime_seconds, algorithm=self.algorithm
+        )
 
     async def destroy_token(self, token: str, user: models.UD) -> None:
         raise StrategyDestroyNotSupportedError(