Should document org_config options for when clauses

[prescod]

This section refers to the org_config object but this object is probably not documented anywhere.

https://cumulusci.readthedocs.io/en/latest/config.html#when-clauses

For example, today I had to ask on Slack about org_config.installed_packages

[RupertBarrow]

Here is what I found by scouring the source code, excluding attributes starting with an underscore, as well as tooling and salesforce_client which sound like internals :

• start_url
• scratch : true indicates the org is a scratch org. False indicates it is a persistent org
• is_person_accounts_enabled : true/false
• installed_packages
• sfdx_alias
• latest_api_version
• name
• org_id
• namespace
• namespaced
• lightning_base_url
• instance_url
• access_token
• username
• user_id
• config_file
• is_multiple_currencies_enabled
• is_advanced_currency_management_enabled
• org_type : eg "Enterprise Edition"
• is_sandbox : true/false
• organization_sobject : whole Organization SObject