Error when trying to start a new session using Selenium driver

Issue

When using wallaby with Selenium driver I get the following error when trying to start a session:

Content-Type header does not indicate utf-8 encoded json: application/json

Code causing the problem

wallaby/lib/wallaby/httpclient.ex

Line 148 in 0fbea3e

[{"Accept", "application/json"}, {"Content-Type", "application/json"}]

Details

Elixir: 1.12.3
Erlang: 24.1
OS: MacOS Big Sur 11.5.2
Webdriver: selenium
Browser (Chrome, Firefox, Safari, etc): Chrome and Firefox
Local or CI: Local

Selenium server version: 4.0.0

The same error happens when trying to start a new session when using other http client with the same headers so my first thought was that it is simply missing the charset. When added to the lib/wallaby/httpclient.ex default headers it started to work as expected.

Having the same problem and I confirm #649 fixes the problem.

Elixir: 1.13.3
Erlang: 24.1.7
OS: MacOS Big Sur 11.6.4
Webdriver: selenium 4.1.3 and geckodriver 0.30.0
Browser (Chrome, Firefox, Safari, etc): Firefox
Local or CI: Local