feat: add concurrency token support for partial variable snapshot updates

[bec-callow-oct]

Background

Adds client support for release and runbook variable snapshot concurrency. Relates to the changes in https://github.com/OctopusDeploy/OctopusDeploy/pull/46160 and https://github.com/OctopusDeploy/OctopusDeploy/pull/46136

Results

The concurrency token can be retrieved from a a release:

release, err := client.Releases.Add(releases.NewRelease(channel.GetID(), proj.GetID(), "1.0.0"))
token := release.VariableSnapshotConcurrencyToken

A new token is generated by the snapshot by name endpoint:

identifiers := []core.VariableIdentifier{{Name: variableName, OwnerID: variableOwnerId}}
afterByName, err := releases.SnapshotVariablesByName(client, release, identifiers, currentToken)

An exception occurs when the concurrency token on the request does not equal the token on the release:

_, err := releases.SnapshotVariablesByName(client, release, identifiers, staleToken)
apiErr := err.(*core.APIError) // apiErr.StatusCode == http.StatusConflict, apiErr.ErrorMessage == "This variable snapshot was changed by someone else since you last loaded it. Please reload and try again."

Code samples for testing

func TestReleaseSnapshotByName(octopusClient *client.Client, project *projects.Project, variable *variables.Variable, release *releases.Release, variableIdentifiers []core.VariableIdentifier) {
	variable.Value = "UpdatedValue1"
	_, err := variables.UpdateSingle(octopusClient, project.SpaceID, project.GetID(), variable)
	if err != nil {
		fmt.Printf("Failed to update the snapshot for release %s. Error: %v\n", release.GetID(), err)
		return
	}

	staleToken := release.VariableSnapshotConcurrencyToken
	updated, err := releases.SnapshotVariablesByName(octopusClient, release, variableIdentifiers, staleToken)
	if err != nil {
		fmt.Printf("Failed to update the snapshot for release %s. Error: %v\n", release.GetID(), err)
		return
	}
	fmt.Printf("Updated the snapshot for release %s\n", updated.GetID())

	variable.Value = "UpdatedValue2"
	_, err = variables.UpdateSingle(octopusClient, project.SpaceID, project.GetID(), variable)
	if err != nil {
		fmt.Printf("Failed to update the snapshot for release %s. Error: %v\n", release.GetID(), err)
		return
	}

	_, err = releases.SnapshotVariablesByName(octopusClient, updated, variableIdentifiers, staleToken)
	if err != nil {
		fmt.Printf("Failed to update the snapshot for release %s. Error: %v\n", release.GetID(), err)
		return
	}
	fmt.Printf("Failed to update the snapshot for release %s. Error: expected an error but none was returned\n", release.GetID())
}

func TestRunbookSnapshotByName(octopusClient *client.Client, project *projects.Project, variable *variables.Variable, runbookSnapshot *runbooks.RunbookSnapshot, variableIdentifiers []core.VariableIdentifier) {
	variable.Value = "UpdatedValue1"
	_, err := variables.UpdateSingle(octopusClient, project.SpaceID, project.GetID(), variable)
	if err != nil {
		fmt.Printf("Failed to update the snapshot for runbook snapshot %s. Error: %v\n", runbookSnapshot.GetID(), err)
		return
	}

	staleToken := runbookSnapshot.VariableSnapshotConcurrencyToken
	updated, err := runbooks.SnapshotVariablesByName(octopusClient, runbookSnapshot, variableIdentifiers, staleToken)
	if err != nil {
		fmt.Printf("Failed to update the snapshot for runbook snapshot %s. Error: %v\n", runbookSnapshot.GetID(), err)
		return
	}
	fmt.Printf("Updated the snapshot for runbook snapshot %s\n", updated.GetID())

	variable.Value = "UpdatedValue2"
	_, err = variables.UpdateSingle(octopusClient, project.SpaceID, project.GetID(), variable)
	if err != nil {
		fmt.Printf("Failed to update the snapshot for runbook snapshot %s. Error: %v\n", runbookSnapshot.GetID(), err)
		return
	}

	_, err = runbooks.SnapshotVariablesByName(octopusClient, updated, variableIdentifiers, staleToken)
	if err != nil {
		fmt.Printf("Failed to update the snapshot for runbook snapshot %s. Error: %v\n", runbookSnapshot.GetID(), err)
		return
	}
	fmt.Printf("Failed to update the snapshot for runbook snapshot %s. Error: expected an error but none was returned\n", runbookSnapshot.GetID())
}

[benPearce1]

I don't think we need to support an array of concurrency tokens here.

[benPearce1]

I have learnt that this is a method of making the parameter optional, and is not uncommon in Go

[benPearce1]

making it an *string would allow it to be optionally null, or a value.

[bec-callow-oct]

I'll change it to *string, that looks cleaner

[benPearce1]

This looks good. Ignore previous comments about the ... operator.