Are plain code challenge methods supported?

[mschwager]

When I hit the openid-configuration endpoint I see the following:

"code_challenge_methods_supported": [
    "plain",
    "S256"
]

And I see the following in the code:

hydra/oauth2/handler.go

Line 509 in 0421fda

CodeChallengeMethodsSupported: []string{"plain", "S256"},

However, I also see this in the code:

hydra/fositex/config.go

Lines 133 to 135 in 0421fda

	func (c *Config) GetEnablePKCEPlainChallengeMethod(context.Context) bool {
	return false
	}

I believe this corresponds to the following fosite code:

https://github.com/ory/fosite/blob/1f27af44d4f83c258c118839ca3171fff08aa77b/handler/pkce/handler.go#L91-L98

So I'm wondering, does hydra support plain code challenges? Is this a bug that the configuration endpoint returns plain?