Merge pull request #1967 from OctopusDeploy/tothegills/concurrencyTag

Describe the Octopus.Task.ConcurrencyTag variable

src/pages/docs/projects/variables/system-variables.md

@@ -1,7 +1,7 @@
 ---
 layout: src/layouts/Default.astro
 pubDate: 2023-01-01
-modDate: 2023-01-01
+modDate: 2023-08-18
 title: System variables
 description: System variables are variables provided by Octopus that can be used in your deployments.
 navOrder: 20
@@ -572,6 +572,7 @@ The following variables can be defined as variables in your project to modify th
 |`OctopusSuppressDuplicateVariableWarning` <br/>Set to `true` to have the duplicate variable message logged as verbose instead of warning. **Do this if you are aware of the duplication and that it isn't causing any issues in your deployment**  (available in version 3.17.0+) | True|
 |`Octopus.Action.Package.RunScripts`  <br/>Set to `false` to prevent scripts inside packages from executing. **Do this if you are aware of the duplication and that it isn't causing any issues in your deployment**  (available in version 4.1.10+) | True|
 |`Octopus.Calamari.CopyWorkingDirectoryIncludingKeyTo`  <br/>Set to a file-path and the Calamari working directory will be copied to the configured location. **Copied files include the one-time key to decrypt sensitive variables** [More details.](/docs/support/copy-working-directory) | `c:\temp\octopus-debug`|
+|`Octopus.Task.ConcurrencyTag` <br/>Octopus will run one task at a time for a given concurrency tag. Set the variable to run tasks in parallel instead of serial or in serial instead of parallel. For example, tenanted deployments run in parallel by default. Removing tenants from the concurrency tag will run them serially: #{Octopus.Project.Id}/#{Octopus.Environment.Id} | #{Octopus.Deployment.Tenant.Id}/#{Octopus.Project.Id}/#{Octopus.Environment.Id}|
 
 ## Learn more