feat: implement stackit git instances (#791)

* feat: implement stackit git instances

* review changes

stackit/internal/services/git/instance/resource_test.go

@@ -0,0 +1,79 @@
+package instance
+
+import (
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/hashicorp/terraform-plugin-framework/types"
+	"github.com/stackitcloud/stackit-sdk-go/core/utils"
+	"github.com/stackitcloud/stackit-sdk-go/services/git"
+)
+
+func TestMapFields(t *testing.T) {
+	tests := []struct {
+		description string
+		input       *git.Instance
+		expected    Model
+		isValid     bool
+	}{
+		{
+			"default_values",
+			&git.Instance{
+				Created: nil,
+				Id:      utils.Ptr("id"),
+				Name:    utils.Ptr("foo"),
+				Url:     utils.Ptr("https://foo.com"),
+				Version: utils.Ptr("v0.0.1"),
+			},
+			Model{
+				Id:         types.StringValue("pid,id"),
+				ProjectId:  types.StringValue("pid"),
+				InstanceId: types.StringValue("id"),
+				Name:       types.StringValue("foo"),
+				Url:        types.StringValue("https://foo.com"),
+				Version:    types.StringValue("v0.0.1"),
+			},
+			true,
+		},
+		{
+			"nil_response",
+			nil,
+			Model{},
+			false,
+		},
+		{
+			"nil_response_2",
+			&git.Instance{},
+			Model{},
+			false,
+		},
+		{
+			"no_id",
+			&git.Instance{
+				Name: utils.Ptr("foo"),
+			},
+			Model{},
+			false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.description, func(t *testing.T) {
+			state := &Model{
+				ProjectId: tt.expected.ProjectId,
+			}
+			err := mapFields(tt.input, state)
+			if !tt.isValid && err == nil {
+				t.Fatalf("Should have failed")
+			}
+			if tt.isValid && err != nil {
+				t.Fatalf("Should not have failed: %v", err)
+			}
+			if tt.isValid {
+				diff := cmp.Diff(state, &tt.expected)
+				if diff != "" {
+					t.Fatalf("Data does not match: %s", diff)
+				}
+			}
+		})
+	}
+}