Add authentication to writes

[adam-hart]

This adds the user's authentication token to any Firebase write request. I also restricted the DB rules in firebase to require auth for writes here https://console.firebase.google.com/project/vivid-inferno-4672/database/rules.

@zendesk/volunteer

[roseleaf]

fixes https://github.com/zendesk/linksf/issues/330

[roseleaf]

for documentation we'll want to include that for the firebase config

{
  "rules": {
    ".read": true,
    ".write": true,
    "organizations": {
      ".indexOn": [
        "id"
      ]
    },
    "services": {
      ".indexOn": [
        "organization"
      ]
    },
    "regular_schedules": {
      ".indexOn": [
        "organization_id"
      ]
    }
  }
}

[roseleaf]

I guess update the rules config file with it