feat: add universities and restaurants (#4)

Features:
- Allow to search for individual resources by their name
- Add new resources and their handler: Universities, Restaurants
- Added new parameter to reverse output order

Reviewed-on: #4
Co-authored-by: bdoerfchen <git@bissendorf.co>
Co-committed-by: bdoerfchen <git@bissendorf.co>

core/handler/universities/uni-handler.go

@@ -0,0 +1,64 @@
+package universities
+
+import (
+	"context"
+	"strings"
+
+	"git.bissendorf.co/bissendorf/unifood/m/v2/core/interfaces"
+	"git.bissendorf.co/bissendorf/unifood/m/v2/core/interfaces/params"
+	"git.bissendorf.co/bissendorf/unifood/m/v2/model/external/stwbremen"
+	"git.bissendorf.co/bissendorf/unifood/m/v2/model/resources"
+	"git.bissendorf.co/bissendorf/unifood/m/v2/util"
+)
+
+type UniversityHandler struct {
+	QueryClient interfaces.QueryClient[stwbremen.RestaurantList]
+}
+
+func (h *UniversityHandler) Get(ctx context.Context, name string, params params.Container) (*interfaces.ResourceList, error) {
+	// Get list of restaurants
+	list, err := getRestaurantList(ctx, h.QueryClient)
+	if err != nil {
+		return nil, err
+	}
+
+	// Group restaurants into universities
+	unis := util.Group(list, func(i *string) (string, string) {
+		parts := strings.SplitN(*i, "/", 2)
+		if len(parts) <= 1 {
+			return *i, *i
+		}
+
+		return parts[0], *i
+	})
+
+	// If name is provided remove all other unis
+	if name != "" {
+		uni, exists := unis[name]
+		unis = make(map[string][]string)
+
+		if exists {
+			unis[name] = uni
+		}
+	}
+
+	// Map into resource
+	uniItems := make([]resources.University, 0, len(unis))
+	for uni, restaurants := range unis {
+		uniItems = append(uniItems, resources.University{
+			Name:        uni,
+			Restaurants: restaurants,
+		})
+	}
+
+	// Return
+	return &interfaces.ResourceList{
+		ItemKind: resources.ResourceUniversity,
+		Items:    util.Transform(uniItems, func(i *resources.University) interfaces.Resource { return i }),
+	}, nil
+
+}
+
+func (h *UniversityHandler) GetParametersForVerb(verb interfaces.Verb) []params.Registration {
+	return []params.Registration{}
+}