feat: GitHub OAuth authentication with embededOAuthAPI

[xbaran4]

Signed-off-by: xbaran4 pbaran@redhat.com

What does this PR do?

Screenshot/screencast of this PR

Enables OAuth flow for GitHub without Keycloak. Using embededOAuthAPI

What issues does this PR fix or reference?

eclipse-che/che#20497

How to test this PR?

1.Deploy quay.io/pbaran/che-server:github10 with devworkspaces.
2. Create GitHub OAuth App in your account. (https://docs.github.com/en/developers/apps/building-oauth-apps/creating-an-oauth-app)
2.1 Application name => Che (But should not matter)
2.2 Homepage URL => $CHE_HOST
2.3 Authorization callback URL => $CHE_HOST/api/oauth/callback
2.4 Register application and generate a new client secret
3. Use your client id and client secret to create k8s github-oauth-config secret:

kubectl apply -f - <<EOF
kind: Secret
apiVersion: v1
metadata:
  name: github-oauth-config
  namespace: <Che namespace. Default eclipse-che> 
  labels:
    app.kubernetes.io/part-of: che.eclipse.org
    app.kubernetes.io/component: oauth-scm-configuration
  annotations:
    che.eclipse.org/oauth-scm-server: github
type: Opaque
data:
  id: <...> 
  secret: <...> 
EOF

(https://www.eclipse.org/che/docs/che-7/administration-guide/configuring-authorization/#configuring-github-oauth_che)
4. Right now you have to restart che-server pod to have the credentials mounted in che.
5. Try to create factory from private repo on your github.

Note: right now you have to have older dashboard version i.e. 7.39.2 because of a bug: eclipse-che/che#20835

PR Checklist

As the author of this Pull Request I made sure that:

• The Eclipse Contributor Agreement is valid
• Code produced is complete
• Code builds without errors
• Tests are covering the bugfix
• The repository devfile is up to date and works
• Sections What issues does this PR fix or reference and How to test this PR completed
• Relevant user documentation updated
• Relevant contributing documentation updated
• CI/CD changes implemented, documented and communicated

Reviewers

Reviewers, please comment how you tested the PR when approving it.

[che-bot]

Can one of the admins verify this patch?

[skabashnyuk]

Works for me