feat: add OpenIn option to coder_app (#15743)

This PR is the coder/coder part of [the open_in parameter
issue](https://github.com/coder/terraform-provider-coder/issues/297)
aiming to add a new optional parameter to choose how to open modules.

This PR is heavily linked [to this
PR](https://github.com/coder/terraform-provider-coder/pull/321).

ℹ️ For now, some integrations tests can not be pushed as it requires a
release on the terraform-provider repo.

coderd/database/dbmem/dbmem.go

@@ -8348,6 +8348,10 @@ func (q *FakeQuerier) InsertWorkspaceApp(_ context.Context, arg database.InsertW
 		arg.SharingLevel = database.AppSharingLevelOwner
 	}
 
+	if arg.OpenIn == "" {
+		arg.OpenIn = database.WorkspaceAppOpenInSlimWindow
+	}
+
 	// nolint:gosimple
 	workspaceApp := database.WorkspaceApp{
 		ID:                   arg.ID,
@@ -8367,6 +8371,7 @@ func (q *FakeQuerier) InsertWorkspaceApp(_ context.Context, arg database.InsertW
 		Health:               arg.Health,
 		Hidden:               arg.Hidden,
 		DisplayOrder:         arg.DisplayOrder,
+		OpenIn:               arg.OpenIn,
 	}
 	q.workspaceApps = append(q.workspaceApps, workspaceApp)
 	return workspaceApp, nil