utils: create 'KeyValue' type

Create a 'KeyValue' type, identical to 'testhelpers.Pair' other than its
field names ('Key'/'Value' vs. 'First'/'Second'). See the comment in the
newly-created 'utils/types.go' for more information about why a new type was
created, rather than moving 'testhelpers.Pair' into 'utils'.

This 'KeyValue' type will be used in future commits as a way of passing
arbitrary configuration options to functions.

Signed-off-by: Victoria Dye <[email protected]>

Author: vdye

internal/utils/types.go

@@ -0,0 +1,22 @@
+package utils
+
+// KeyValue is very similar to testhelpers.Pair. Consider unifying on a single
+// 'utils.Pair' if https://github.com/golang/go/issues/52654 is ever
+// implemented. With that, we can alias 'utils.NewPair' in 'testhelpers' with:
+//
+// func NewPair = utils.NewPair
+//
+// and avoid the need to either prefix all 'NewPair' calls with 'utils.' (since
+// we don't want to dot-import 'utils' either).
+
+type KeyValue[T any, R any] struct {
+	Key   T
+	Value R
+}
+
+func NewKeyValue[T any, R any](key T, value R) KeyValue[T, R] {
+	return KeyValue[T, R]{
+		Key:   key,
+		Value: value,
+	}
+}