Running in rootless docker is nonfunctional with host filesystem bind mounts due to overriden user ID inside container

[tazz4843]

I'm using a docker-compose.yml file to orchestrate setup. Data has not been showing up in Influx since I started trying to set it up. After several hours of digging, I noticed the bind mounts I had set up in the docker-compose.yml file had an unusual user ID attached:

as sudo niko@niko-desktop docker-compose-influxdb-grafana > ls -lh data/
total 8.0K
drwxr-xr-x 1 niko   niko 62 Nov  1 15:34 grafana/
drwx------ 1 100999 niko 40 Nov  1 15:37 influx/
drwxrwxr-x 1 100999 niko 28 Nov  1 14:41 influx-config/

This persists despite user ID 0 being forced in the docker-compose.yml file, which maps to my true user on the host system in a rootless setup:

version: '2'
services:
  influxdb:
    image: influxdb:latest
    ports:
      - '8086:8086'
    user: "0:0"
    volumes:
      - ./data/influx:/var/lib/influxdb2
      - ./data/influx-config:/etc/influxdb2
    environment:
      - DOCKER_INFLUXDB_INIT_MODE=setup
      - DOCKER_INFLUXDB_INIT_USERNAME=redacted
      - DOCKER_INFLUXDB_INIT_PASSWORD=redacted
      - DOCKER_INFLUXDB_INIT_ORG=weather
      - DOCKER_INFLUXDB_INIT_BUCKET=main
  grafana:
    image: grafana/grafana:latest
    ports:
      - '3000:3000'
    user: "0:0"
    volumes:
      - ./data/grafana:/var/lib/grafana
      - ./grafana-provisioning/:/etc/grafana/provisioning
    depends_on:
      - influxdb
    environment:
      - GF_SECURITY_ADMIN_USER=${GRAFANA_USERNAME}
      - GF_SECURITY_ADMIN_PASSWORD=${GRAFANA_PASSWORD}

Grafana complains once at startup that it's running as a privileged user, when in actuality it is running as my user. However, InfluxDB fails silently with no permissions errors or anything of the sort mentioned in logs. The only reason I eventually figured this out was because of a GitHub issue: itzg/docker-minecraft-server#1934 (comment)