Add OAuth2/Space client authentication

Subsystem Client

Is your feature request related to a problem? Please describe. There is no oauth2 client authentication, and especially JetBrains Space auth

Describe the solution you’d like I’d like to have smth like

val spaceClient = client.config {
    Auth {
       Space(clientId, clientSecret) 
    }
}

actually to authenticate in Space I have to do smth like

private data class AccessToken(val token_type: String, val expires_in: Int, val access_token: String)

private suspend fun issueAccessToken(endpoint: String, clientId: String, clientSecret: String): AccessToken {
        return client.submitForm(
            url = "${endpoint}/oauth/token",
            formParameters = Parameters.build {
                append("grant_type", "client_credentials")
                append("scope", "**")
            }
        ) {
            header(
                HttpHeaders.Authorization,
                HttpAuthHeader.Single(
                    AuthScheme.Basic,
                    String(Base64.getEncoder().encode("$clientId:$clientSecret".toByteArray()))
                ).render()
            )
        }
    }

and later on for each query use

private fun HttpRequestBuilder.authHeader() {
        header(
            HttpHeaders.Authorization,
            HttpAuthHeader.Single(issueAccessToken.token_type, issueAccessToken.access_token).render()
        )
    }

Motivation to include to ktor OAuth2 is quite common auth way

[fullkomnun]

Is there any update regarding this issue?

[hardysim]

To crosslink the progress:

• #1740 contains the OAuthAuthProvider but was only merged into a private branch by @e5l
• #1733 contains an additional constant AuthScheme.Bearer which is needed by OAuthAuthProvider but is not merged yet
• I’ve used both in production since I’ve posted both and they’re working fine so I’d be happy if both can me accepted and added to the master-branch.