How do I add custom entities to when using the Kubernetes Ingress Controller with a postgres database?

Title. I have Kong running with the Kubernetes Ingress Controller. I already have a working custom plugin. I tried to add a migrations folder to my plugin files with the appropriate migrations in it but subdirectories get ignored by kubectl create configmap and the -R flag doesn't work.

Unfortunately this is not supported currently. The way you work around this limitation is by creating a volume in the YAML in order to define the path for the files you have in subfolders like so:

apiVersion: v1
kind: ConfigMap
metadata:
   name: testconfig
data:
  file1: |
    This is file1
  file2: |
    This is file2 in subdir directory
---

And then in the volume part of the YAML you would specify the path to the files with their names

  volumes:
    - name: config-volume
      configMap:
        name: testconfig
        items:
        - key: file2
          path: subdir/file2
        - key: file1
          path: file1

You can do this with initContainers and emptyDir mounts by passing the info from the initContainer to the application as described here