Document the org_config Object (#3490)

To fix #2424, I have created a document called `org_config.md` under
docs, and added this paragraph to the `reference.md` chapter.

At the same time, I fixed the name of the env-var-reference chapter
which was incorrectly referenced in `reference.md` and, thus, did not
appear in the generated documentation.

I scoured the source code for these attributes, leaving out the
attributes with names starting with an underscore, as well as
`salesforce_client` and `tooling` which sound like reserved for internal
use.
I guessed the use of most of the attributes from their name. When in
doubt, I left attributes with unknown use in a separate list.

---------

Co-authored-by: James Estevez <jestevez@salesforce.com>
Co-authored-by: James Estevez <j@jstvz.dev>

Author: RupertBarrow

AUTHORS.rst

@@ -38,3 +38,4 @@ For example:
 * Gustavo Tandeciarz (dcinzona)
 * Chandler Anderson (zenibako)
 * Ben French (BenjaminFrench)
+* Rupert Barrow (rupertbarrow)

docs/org_config-reference.md

@@ -0,0 +1,59 @@
+# org_config Object Reference
+
+The `org_config` object can be used in the `cumulusci.yml` file to read a large number number of attributes of the Salesforce org currently used. For example, in a [custom flow step](https://cumulusci.readthedocs.io/en/stable/config.html#add-a-flow-step), you can use a `when` clause to adapt the behavior of the new step to the type of org (scratch org or not) by referencing the `org_config.scratch` attribute.
+
+The following information is documented here in the application's source code :
+https://github.com/SFDO-Tooling/CumulusCI/blob/main/cumulusci/core/config/org_config.py
+
+## org_config Object Attributes
+
+-   `access_token` : access token currently used to authenticate with Salesforce
+-   `installed_packages` : comma-separated list of package names; a `dict` mapping a namespace or metadata package ID (starts with `033`) to the installed package version(s) matching that identifier. All values are lists, because multiple second-generation packages may be installed with the same namespace. The beta version of a package is represented as "1.2.3b5", where 5 is the build number.
+-   `instance_url` : eg `https://crazy-demo.scratch.my.salesforce.com`
+-   `instance_name` : eg `crazy-demo`
+-   `is_advanced_currency_management_enabled` : `true` or `false`
+-   `is_multiple_currencies_enabled`: `true` or `false`
+-   `is_person_accounts_enabled` : `true` or `false`
+-   `is_sandbox` : `true` if the org is a sandbox
+-   `is_survey_advanced_features_enabled`: `true` or `false`
+-   `lightning_base_url` : base url ending with `.lightning.force.com`
+-   `namespace` : namespace of the org
+-   `namespaced` : `true` if the org has a namespace
+-   `org_id` : Organization ID of the Salesforce org
+-   `org_type` : eg "Enterprise Edition" or "Developer Edition"
+-   `organization_sobject` : The Organization object (see the [Salesforce documentation for the Organization SObject](https://developer.salesforce.com/docs/atlas.en-us.object_reference.meta/object_reference/sforce_api_objects_organization.htm)) for the org.
+-   `scratch` : `True` when the org is a scratch org.
+-   `start_url`: the frontdoor URL that results in an instant login, like `https://mydomain.my.salesforce.com/secur/frontdoor.jsp?sid=...`
+-   `user_id` : user ID of the current Salesforce user
+-   `userinfo`: user OAuth2 information (see https://help.salesforce.com/s/articleView?id=sf.remoteaccess_using_userinfo_endpoint.htm)
+-   `username` : username of the current Salesforce user
+
+## Other org_config Object Attributes
+
+-   `config_file`
+-   `config_name`
+-   `latest_api_version`
+-   `name`
+-   `salesforce_client`
+-   `sfdx_alias`
+
+## org_config Object Methods
+
+-   `has_minimum_package_version(package_identifier, version_identifier)`: `true` if the org has a version of the specified package that is equal to or newer than the supplied version identifier.
+    The package identifier may be either a namespace or a `033` MetadataPackage ID.
+    The version identifier should be in "1.2.3" or "1.2.3b4" format.
+
+    `when` expressions can use the `has_minimum_package_version` method to check if a package is installed with a sufficient version.
+
+    For example:
+    `when: org_config.has_minimum_package_version("namespace", "1.0")`
+
+    See a real-life example here : https://trailhead.salesforce.com/fr/trailblazer-community/feed/0D54V00007erukZSAQ
+
+-   `get_community_info(community_name, force_refresh=False)`: Returns the community information for the given community (see https://developer.salesforce.com/docs/atlas.en-us.chatterapi.meta/chatterapi/connect_responses_community.htm)
+
+    An API call will be made the first time this method is used,
+    and the return values will be cached. Subsequent calls will
+    not call the API unless the requested community name is not in
+    the cached results, or unless the force_refresh parameter is
+    set to True

docs/reference.md

@@ -8,5 +8,6 @@ maxdepth: 1
 cheat-sheet
 cumulusci_tasks
 flows
-env_var_reference
+env-var-reference
+org_config-reference
 ```