Add support to authorization middleware for jwt based Authorizer

[GeorgeMac]

Add support for deserialization / validation of JWT based authorizer within authentication middleware:
https://github.com/influxdata/influxdb/blob/master/http/authentication_middleware.go

Steps:

1. When attempting to deserialize a token (given we have a JWT secret), first attempt to deserialize it as a JWT token:
   

   influxdb/http/authentication_middleware.go

   Lines 104 to 116 in feda6dc

   	func (h *AuthenticationHandler) extractAuthorization(ctx context.Context, r *http.Request) (context.Context, error) {
   	t, err := GetToken(r)
   	if err != nil {
   	return ctx, err
   	}
   	a, err := h.AuthorizationService.FindAuthorizationByToken(ctx, t)
   	if err != nil {
   	return ctx, err
   	}
   	return platcontext.SetAuthorizer(ctx, a), nil
   	}

2. If an error is returned because it is not a well formed token or no JWT secret exists then attempt to find authorization using the token as we currently do so.
3. If an error is returned because the token is well-formed, however, it is invalid (invalid signature, expired and so on) then return the error.
4. If the token is valid and the permissions can be deserialized then set the authorizer on the context.

Success Criteria

When configured with a JWT secret, API actions can be triggered using a well formed token. e.g. a token with permissions with write action for a specific bucket within a specific org can be generated using a secret and then used to trigger a write.