Don't allow special characters in app names

Basically someone ran into an issue because they tried to do this in ruby:

```
Pyroscope.configure do |config|
config.application_name = "xyz-graphql - #{Rails.env}"
config.server_address = "https://profiles-prod-001.grafana.net/"
config.basic_auth_username = "0000000"
config.basic_auth_password = ENV["BPUB_GRAFANA_TOKEN"]
end
```

and didn't realize that spaces were not allowed in the app name

We should update all of our integrations to warn people if they try to put a special character in the function name. or sanitize the app name when they send the data

Same may be true for tag values. Not sure if it's better to do this at ingest or on the client side