Fix repository_property validation and docs

  - Add ValidateFunc to include.source field for consistency with exclude
  - Update docs to mention repository_property as third targeting option
  - Fix missing space in documentation

Author: Moser-ss

github/resource_github_organization_ruleset.go

@@ -144,10 +144,11 @@ func resourceGithubOrganizationRuleset() *schema.Resource {
 													},
 												},
 												"source": {
-													Type:        schema.TypeString,
-													Optional:    true,
-													Description: "The source of the repository property. Defaults to 'custom' if not specified. Can be one of: custom, system",
-													Default:     "custom",
+													Type:         schema.TypeString,
+													Optional:     true,
+													Description:  "The source of the repository property. Defaults to 'custom' if not specified. Can be one of: custom, system",
+													Default:      "custom",
+													ValidateFunc: validation.StringInSlice([]string{"custom", "system"}, false),
 												},
 											},
 										},

website/docs/r/organization_ruleset.html.markdown

@@ -310,7 +310,7 @@ The `rules` block supports the following:
 - `repository_name` (Optional) (Block List, Max: 1) Conflicts with `repository_id` and `repository_property`. (see [below for nested schema](#conditions.repository_name))
 - `repository_property` (Optional) (Block List, Max: 1) Conflicts with `repository_id` and `repository_name`. (see [below for nested schema](#conditions.repository_property))
 
-One of `repository_id` and `repository_name` must be set for the rule to target any repositories.
+One of `repository_id`, `repository_name`, or `repository_property` must be set for the rule to target any repositories.
 
 #### conditions.ref_name ####
 
@@ -328,7 +328,7 @@ One of `repository_id` and `repository_name` must be set for the rule to target
 
 - `include` - (Optional) (List of Repository Properties) The repository properties and values to include. All of these properties must match for the condition to pass. (see [below for nested schema](#conditions.repository_property.properties))
 
-- `exclude` - (Optional) (List of Repository Properties) The repository properties and values to exclude. The condition will not pass if any of these properties match.(see [below for nested schema](#conditions.repository_property.properties))
+- `exclude` - (Optional) (List of Repository Properties) The repository properties and values to exclude. The condition will not pass if any of these properties match. (see [below for nested schema](#conditions.repository_property.properties))
 
 #### conditions.repository_property.properties ####