Query builder (#10104)

* add query builder to facilitate dynamic SQL construction

* leverage query builder to refactor user store

This is partially setup work for MM-13120, but merged to master to avoid
further conflicts.

* fix unrelated unit test breakage

* documentation tweaks

* Apply suggestions from code review

Co-Authored-By: lieut-data <jesse.hallam@gmail.com>

* prefer comma separated case options to fallthrough

* vendor github.com/Masterminds/squirrel and deps

* switch to using github.com/Masterminds/squirrel

* rm querybuilder

vendor/github.com/lann/builder/reflect.go

@@ -0,0 +1,24 @@
+package builder
+
+import "reflect"
+
+func convert(from interface{}, to interface{}) interface{} {
+	return reflect.
+		ValueOf(from).
+		Convert(reflect.TypeOf(to)).
+		Interface()
+}
+
+func forEach(s interface{}, f func(interface{})) {
+	val := reflect.ValueOf(s)
+
+	kind := val.Kind()
+	if kind != reflect.Slice && kind != reflect.Array {
+		panic(&reflect.ValueError{Method: "builder.forEach", Kind: kind})
+	}
+
+	l := val.Len()
+	for i := 0; i < l; i++ {
+		f(val.Index(i).Interface())
+	}
+}