Add environment variables for OIDC token service (#674)

Resurrecting [this PR](https://gitea.com/gitea/act_runner/pulls/272) (a dependency of [this one](go-gitea/gitea#33945)) after the original author [lost motivation](go-gitea/gitea#25664 (comment)) - though, to be clear, all credit belongs to them, and all blame for mistakes or misunderstandings to me.

Co-authored-by: Søren L. Hansen <[email protected]>
Reviewed-on: https://gitea.com/gitea/act_runner/pulls/674
Reviewed-by: ChristopherHX <[email protected]>
Reviewed-by: Lunny Xiao <[email protected]>
Co-authored-by: Jack Jackson <[email protected]>
Co-committed-by: Jack Jackson <[email protected]>

Author: 2 people

internal/app/run/runner.go

@@ -163,6 +163,12 @@ func (r *Runner) run(ctx context.Context, task *runnerv1.Task, reporter *report.
 		preset.Token = t
 	}
 
+	if actionsIdTokenRequestUrl := taskContext["actions_id_token_request_url"].GetStringValue(); actionsIdTokenRequestUrl != "" {
+		r.envs["ACTIONS_ID_TOKEN_REQUEST_URL"] = actionsIdTokenRequestUrl
+		r.envs["ACTIONS_ID_TOKEN_REQUEST_TOKEN"] = taskContext["actions_id_token_request_token"].GetStringValue()
+		task.Secrets["ACTIONS_ID_TOKEN_REQUEST_TOKEN"] = r.envs["ACTIONS_ID_TOKEN_REQUEST_TOKEN"]
+	}
+
 	giteaRuntimeToken := taskContext["gitea_runtime_token"].GetStringValue()
 	if giteaRuntimeToken == "" {
 		// use task token to action api token for previous Gitea Server Versions