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/Masterminds/squirrel/statement.go

@@ -0,0 +1,83 @@
+package squirrel
+
+import "github.com/lann/builder"
+
+// StatementBuilderType is the type of StatementBuilder.
+type StatementBuilderType builder.Builder
+
+// Select returns a SelectBuilder for this StatementBuilderType.
+func (b StatementBuilderType) Select(columns ...string) SelectBuilder {
+	return SelectBuilder(b).Columns(columns...)
+}
+
+// Insert returns a InsertBuilder for this StatementBuilderType.
+func (b StatementBuilderType) Insert(into string) InsertBuilder {
+	return InsertBuilder(b).Into(into)
+}
+
+// Update returns a UpdateBuilder for this StatementBuilderType.
+func (b StatementBuilderType) Update(table string) UpdateBuilder {
+	return UpdateBuilder(b).Table(table)
+}
+
+// Delete returns a DeleteBuilder for this StatementBuilderType.
+func (b StatementBuilderType) Delete(from string) DeleteBuilder {
+	return DeleteBuilder(b).From(from)
+}
+
+// PlaceholderFormat sets the PlaceholderFormat field for any child builders.
+func (b StatementBuilderType) PlaceholderFormat(f PlaceholderFormat) StatementBuilderType {
+	return builder.Set(b, "PlaceholderFormat", f).(StatementBuilderType)
+}
+
+// RunWith sets the RunWith field for any child builders.
+func (b StatementBuilderType) RunWith(runner BaseRunner) StatementBuilderType {
+	return setRunWith(b, runner).(StatementBuilderType)
+}
+
+// StatementBuilder is a parent builder for other builders, e.g. SelectBuilder.
+var StatementBuilder = StatementBuilderType(builder.EmptyBuilder).PlaceholderFormat(Question)
+
+// Select returns a new SelectBuilder, optionally setting some result columns.
+//
+// See SelectBuilder.Columns.
+func Select(columns ...string) SelectBuilder {
+	return StatementBuilder.Select(columns...)
+}
+
+// Insert returns a new InsertBuilder with the given table name.
+//
+// See InsertBuilder.Into.
+func Insert(into string) InsertBuilder {
+	return StatementBuilder.Insert(into)
+}
+
+// Update returns a new UpdateBuilder with the given table name.
+//
+// See UpdateBuilder.Table.
+func Update(table string) UpdateBuilder {
+	return StatementBuilder.Update(table)
+}
+
+// Delete returns a new DeleteBuilder with the given table name.
+//
+// See DeleteBuilder.Table.
+func Delete(from string) DeleteBuilder {
+	return StatementBuilder.Delete(from)
+}
+
+// Case returns a new CaseBuilder
+// "what" represents case value
+func Case(what ...interface{}) CaseBuilder {
+	b := CaseBuilder(builder.EmptyBuilder)
+
+	switch len(what) {
+	case 0:
+	case 1:
+		b = b.what(what[0])
+	default:
+		b = b.what(newPart(what[0], what[1:]...))
+
+	}
+	return b
+}