URL Encoding/Decoding Differences between JS and Rust client

[nataliepopescu]

To encode the "device_id" search param when getting an otkey from the server, the JS client uses encodeURIComponent and the Rust client uses urlencoding::encode, which seem to encode strings using the same scheme. For example, both methods encode
fWJSs3OTKX/su3jJMzaqc7bwobE2I+7Q/+xT8Fz7mB4
into
fWJSs3OTKX%2Fsu3jJMzaqc7bwobE2I%2B7Q%2F%2BxT8Fz7mB4,
e.g., a %AB hex-encoding scheme.

However, the go server receives
fWJSs3OTKX%252Fsu3jJMzaqc7bwobE2I%252B7Q%252F%252BxT8Fz7
as the encoded string from the JS client (evidently a %ABCD hex-encoding scheme), while still receiving
fWJSs3OTKX%2Fsu3jJMzaqc7bwobE2I%2B7Q%2F%2BxT8Fz7mB4
from the Rust client.

A temporary fix removes one round of decoding from the server for Rust clients, but ideally both Rust and JS clients would use the same server, so I don't see this being a long-term solution.