chore(docs): add possible values for security group rule protocol (#857)

relates to #816

stackit/internal/utils/utils.go

@@ -144,3 +144,12 @@ func LogError(ctx context.Context, inputDiags *diag.Diagnostics, err error, summ
 	}
 	core.LogAndAddError(ctx, inputDiags, summary, description)
 }
+
+// FormatPossibleValues formats a slice into a comma-separated-list for usage in the provider docs
+func FormatPossibleValues(values []string) string {
+	var formattedValues []string
+	for _, value := range values {
+		formattedValues = append(formattedValues, fmt.Sprintf("`%v`", value))
+	}
+	return fmt.Sprintf("Possible values are: %s.", strings.Join(formattedValues, ", "))
+}

stackit/internal/utils/utils_test.go

@@ -1,6 +1,7 @@
 package utils
 
 import (
+	"fmt"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
@@ -268,3 +269,38 @@ func TestIsLegacyProjectRole(t *testing.T) {
 		})
 	}
 }
+
+func TestFormatPossibleValues(t *testing.T) {
+	gotPrefix := "Possible values are:"
+
+	type args struct {
+		values []string
+	}
+	tests := []struct {
+		name string
+		args args
+		want string
+	}{
+		{
+			name: "single string value",
+			args: args{
+				values: []string{"foo"},
+			},
+			want: fmt.Sprintf("%s `foo`.", gotPrefix),
+		},
+		{
+			name: "multiple string value",
+			args: args{
+				values: []string{"foo", "bar", "trololol"},
+			},
+			want: fmt.Sprintf("%s `foo`, `bar`, `trololol`.", gotPrefix),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := FormatPossibleValues(tt.args.values); got != tt.want {
+				t.Errorf("FormatPossibleValues() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}