This assumes you have used the REST API to obtain an OAuth bearer token. Let's say the bearer token is sha256~0Rs__hPuXmBD3TJTXNDisC7wRBN-nrFnYTxgdBrFT-U.

Let's say you want to delete the project named "my-project". You probably first want to issue a GET request to see if my-project exists.

curl
--insecure
--request GET
--header "Accept: application/json"
--header "Authorization: Bearer sha256~0Rs__hPuXmBD3TJTXNDisC7wRBN-nrFnYTxgdBrFT-U"
--url "https://api.openshift.example.com:6443/api/v1/namespaces/my-project"

If the project exists, something like this should be returned.

{
  "kind": "NamespaceList",
  "apiVersion": "v1",
  "metadata": {
    "selfLink": "/api/v1/namespaces",
    "resourceVersion": "637674757"
  },
  "items": [
    {
      "metadata": {
        "name": "foo",
        "selfLink": "/api/v1/namespaces/foo",
        "uid": "d0022a41-0165-4734-b468-948fa40a93a9",
        "resourceVersion": "568396970",
        "creationTimestamp": "2020-10-20T13:40:08Z"

Here is how you could then delete my-project. The status of the project should be Terminating for a bit, and then the project should be deleted.

curl
--insecure
--request DELETE
--header "Accept: application/json"
--header "Content-Type: application/yaml"
--header "Authorization: Bearer sha256~0Rs__hPuXmBD3TJTXNDisC7wRBN-nrFnYTxgdBrFT-U"
--url "https://api.openshift.example.com:6443/api/v1/namespaces/my-project"