Local queries (#641)

* Read local queries from pgweb home directory
* Refactor local query functionality
* Allow picking local query in the query tab
* WIP
* Disable local query dropdown during execution
* Only allow local queries running in a single session mode
* Add middleware to enforce local query endpoint availability
* Fix query check
* Add query store tests
* Make query store errors portable
* Skip building specific tests on windows

pkg/queries/query.go

@@ -0,0 +1,23 @@
+package queries
+
+type Query struct {
+	ID   string
+	Path string
+	Meta *Metadata
+	Data string
+}
+
+// IsPermitted returns true if a query is allowed to execute for a given db context
+func (q Query) IsPermitted(host, user, database, mode string) bool {
+	// All fields must be provided for matching
+	if q.Meta == nil || host == "" || user == "" || database == "" || mode == "" {
+		return false
+	}
+
+	meta := q.Meta
+
+	return meta.Host.matches(host) &&
+		meta.User.matches(user) &&
+		meta.Database.matches(database) &&
+		meta.Mode.matches(mode)
+}