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/squirrel_ctx.go

@@ -0,0 +1,61 @@
+// +build go1.8
+
+package squirrel
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+)
+
+// NoContextSupport is returned if a db doesn't support Context.
+var NoContextSupport = errors.New("DB does not support Context")
+
+// ExecerContext is the interface that wraps the ExecContext method.
+//
+// Exec executes the given query as implemented by database/sql.ExecContext.
+type ExecerContext interface {
+	ExecContext(ctx context.Context, query string, args ...interface{}) (sql.Result, error)
+}
+
+// QueryerContext is the interface that wraps the QueryContext method.
+//
+// QueryContext executes the given query as implemented by database/sql.QueryContext.
+type QueryerContext interface {
+	QueryContext(ctx context.Context, query string, args ...interface{}) (*sql.Rows, error)
+}
+
+// QueryRowerContext is the interface that wraps the QueryRowContext method.
+//
+// QueryRowContext executes the given query as implemented by database/sql.QueryRowContext.
+type QueryRowerContext interface {
+	QueryRowContext(ctx context.Context, query string, args ...interface{}) RowScanner
+}
+
+func (r *stdsqlRunner) QueryRowContext(ctx context.Context, query string, args ...interface{}) RowScanner {
+	return r.stdsql.QueryRowContext(ctx, query, args...)
+}
+
+// ExecContextWith ExecContexts the SQL returned by s with db.
+func ExecContextWith(ctx context.Context, db ExecerContext, s Sqlizer) (res sql.Result, err error) {
+	query, args, err := s.ToSql()
+	if err != nil {
+		return
+	}
+	return db.ExecContext(ctx, query, args...)
+}
+
+// QueryContextWith QueryContexts the SQL returned by s with db.
+func QueryContextWith(ctx context.Context, db QueryerContext, s Sqlizer) (rows *sql.Rows, err error) {
+	query, args, err := s.ToSql()
+	if err != nil {
+		return
+	}
+	return db.QueryContext(ctx, query, args...)
+}
+
+// QueryRowContextWith QueryRowContexts the SQL returned by s with db.
+func QueryRowContextWith(ctx context.Context, db QueryRowerContext, s Sqlizer) RowScanner {
+	query, args, err := s.ToSql()
+	return &Row{RowScanner: db.QueryRowContext(ctx, query, args...), err: err}
+}