trailing comma fix for oidc

[jpetrucciani]

this makes it so the comma is only added in the case that you have those env vars specified, prepending it so that we don't have the case where it fails to parse

should fix #7

[fiftin]

Did you test the PR?

[jpetrucciani]

I've tested this rendering out locally with and without the forwarded_env_vars, and it now generates valid/parse-able JSON in both cases for me. I used my fork + branch and ran:

helm dependency build ./stable/semaphore/

helm template -f values.yaml semaphore ./stable/semaphore/   # tested without `forwarded_env_vars`, then added and ran again

values.yaml:

oidc:
  enable: true
  providers:
    google:
      client_id: '...'
      client_secret: '...'
      color: 'blue'
      display_name: 'sign in with google'
      icon: 'google'
      name_claim: 'name'
      provider_url: 'https://accounts.google.com'
      redirect_url: 'https://website.com/api/auth/oidc/google/redirect'
      username_claim: '|'

# this was added after the first run
config:
  forwarded_env_vars: ["TEST"]