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/field.go

@@ -0,0 +1,43 @@
+package queries
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+type field struct {
+	value string
+	re    *regexp.Regexp
+}
+
+func (f field) String() string {
+	return f.value
+}
+
+func (f field) matches(input string) bool {
+	if f.re != nil {
+		return f.re.MatchString(input)
+	}
+	return f.value == input
+}
+
+func newField(value string) (field, error) {
+	f := field{value: value}
+
+	if value == "*" { // match everything
+		f.re = reMatchAll
+	} else if reExpression.MatchString(value) { // match by given expression
+		// Make writing expressions easier for values like "foo_*"
+		if strings.Count(value, "*") == 1 {
+			value = strings.Replace(value, "*", "(.+)", 1)
+		}
+		re, err := regexp.Compile(fmt.Sprintf("^%s$", value))
+		if err != nil {
+			return f, err
+		}
+		f.re = re
+	}
+
+	return f, nil
+}