MM-43144: Add teams loader (#19960)

```release-note
NONE
```

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

api4/graphql.go

@@ -65,6 +65,7 @@ const (
 	webCtx            ctxKey = 0
 	rolesLoaderCtx    ctxKey = 1
 	channelsLoaderCtx ctxKey = 2
+	teamsLoaderCtx    ctxKey = 3
 )
 
 const loaderBatchCapacity = 200
@@ -107,6 +108,9 @@ func (api *API) graphQL(c *Context, w http.ResponseWriter, r *http.Request) {
 	channelsLoader := dataloader.NewBatchedLoader(graphQLChannelsLoader, dataloader.WithBatchCapacity(loaderBatchCapacity))
 	reqCtx = context.WithValue(reqCtx, channelsLoaderCtx, channelsLoader)
 
+	teamsLoader := dataloader.NewBatchedLoader(graphQLTeamsLoader, dataloader.WithBatchCapacity(loaderBatchCapacity))
+	reqCtx = context.WithValue(reqCtx, teamsLoaderCtx, teamsLoader)
+
 	response = api.schema.Exec(reqCtx,
 		params.Query,
 		params.OperationName,

api4/resolver.go

@@ -303,3 +303,12 @@ func getChannelsLoader(ctx context.Context) (*dataloader.Loader, error) {
 	}
 	return l, nil
 }
+
+// getTeamsLoader returns the teams loader out of the context.
+func getTeamsLoader(ctx context.Context) (*dataloader.Loader, error) {
+	l, ok := ctx.Value(teamsLoaderCtx).(*dataloader.Loader)
+	if !ok {
+		return nil, errors.New("no dataloader.Loader found in context")
+	}
+	return l, nil
+}

api4/resolver_team.go

@@ -5,8 +5,12 @@ package api4
 
 import (
 	"context"
+	"fmt"
+
+	"github.com/graph-gophers/dataloader/v6"
 
 	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/web"
 )
 
 func getGraphQLTeam(ctx context.Context, id string) (*model.Team, error) {
@@ -15,11 +19,18 @@ func getGraphQLTeam(ctx context.Context, id string) (*model.Team, error) {
 		return nil, err
 	}
 
-	team, appErr := c.App.GetTeam(id)
-	if appErr != nil {
-		return nil, appErr
+	loader, err := getTeamsLoader(ctx)
+	if err != nil {
+		return nil, err
 	}
 
+	thunk := loader.Load(ctx, dataloader.StringKey(id))
+	result, err := thunk()
+	if err != nil {
+		return nil, err
+	}
+	team := result.(*model.Team)
+
 	if (!team.AllowOpenInvite || team.Type != model.TeamOpen) &&
 		!c.App.SessionHasPermissionToTeam(*c.AppContext.Session(), team.Id, model.PermissionViewTeam) {
 		c.SetPermissionError(model.PermissionViewTeam)
@@ -29,3 +40,53 @@ func getGraphQLTeam(ctx context.Context, id string) (*model.Team, error) {
 	team = c.App.SanitizeTeam(*c.AppContext.Session(), team)
 	return team, nil
 }
+
+func graphQLTeamsLoader(ctx context.Context, keys dataloader.Keys) []*dataloader.Result {
+	stringKeys := keys.Keys()
+	result := make([]*dataloader.Result, len(stringKeys))
+
+	c, err := getCtx(ctx)
+	if err != nil {
+		for i := range result {
+			result[i] = &dataloader.Result{Error: err}
+		}
+		return result
+	}
+
+	teams, err := getGraphQLTeams(c, stringKeys)
+	if err != nil {
+		for i := range result {
+			result[i] = &dataloader.Result{Error: err}
+		}
+		return result
+	}
+
+	for i, ch := range teams {
+		result[i] = &dataloader.Result{Data: ch}
+	}
+	return result
+}
+
+func getGraphQLTeams(c *web.Context, teamIDs []string) ([]*model.Team, error) {
+	teams, appErr := c.App.GetTeams(teamIDs)
+	if appErr != nil {
+		return nil, appErr
+	}
+
+	if len(teams) != len(teamIDs) {
+		return nil, fmt.Errorf("All teams were not found. Requested %d; Found %d", len(teamIDs), len(teams))
+	}
+
+	// The teams need to be in the exact same order as the input slice.
+	tmp := make(map[string]*model.Team)
+	for _, ch := range teams {
+		tmp[ch.Id] = ch
+	}
+
+	// We reuse the same slice and just rewrite the teams.
+	for i, id := range teamIDs {
+		teams[i] = tmp[id]
+	}
+
+	return teams, nil
+}