cloudapi: use Recover middleware to handle panics

recover from panics such as out-of-bounds array access & nil
pointer access, print a stack trace and return 5xx error
instead of the service crashing and relying on Execution
framework to handle crashes

vendor/github.com/labstack/echo/v4/middleware/middleware.go

@@ -0,0 +1,89 @@
+package middleware
+
+import (
+	"net/http"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"github.com/labstack/echo/v4"
+)
+
+type (
+	// Skipper defines a function to skip middleware. Returning true skips processing
+	// the middleware.
+	Skipper func(echo.Context) bool
+
+	// BeforeFunc defines a function which is executed just before the middleware.
+	BeforeFunc func(echo.Context)
+)
+
+func captureTokens(pattern *regexp.Regexp, input string) *strings.Replacer {
+	groups := pattern.FindAllStringSubmatch(input, -1)
+	if groups == nil {
+		return nil
+	}
+	values := groups[0][1:]
+	replace := make([]string, 2*len(values))
+	for i, v := range values {
+		j := 2 * i
+		replace[j] = "$" + strconv.Itoa(i+1)
+		replace[j+1] = v
+	}
+	return strings.NewReplacer(replace...)
+}
+
+func rewriteRulesRegex(rewrite map[string]string) map[*regexp.Regexp]string {
+	// Initialize
+	rulesRegex := map[*regexp.Regexp]string{}
+	for k, v := range rewrite {
+		k = regexp.QuoteMeta(k)
+		k = strings.Replace(k, `\*`, "(.*?)", -1)
+		if strings.HasPrefix(k, `\^`) {
+			k = strings.Replace(k, `\^`, "^", -1)
+		}
+		k = k + "$"
+		rulesRegex[regexp.MustCompile(k)] = v
+	}
+	return rulesRegex
+}
+
+func rewriteURL(rewriteRegex map[*regexp.Regexp]string, req *http.Request) error {
+	if len(rewriteRegex) == 0 {
+		return nil
+	}
+
+	// Depending how HTTP request is sent RequestURI could contain Scheme://Host/path or be just /path.
+	// We only want to use path part for rewriting and therefore trim prefix if it exists
+	rawURI := req.RequestURI
+	if rawURI != "" && rawURI[0] != '/' {
+		prefix := ""
+		if req.URL.Scheme != "" {
+			prefix = req.URL.Scheme + "://"
+		}
+		if req.URL.Host != "" {
+			prefix += req.URL.Host // host or host:port
+		}
+		if prefix != "" {
+			rawURI = strings.TrimPrefix(rawURI, prefix)
+		}
+	}
+
+	for k, v := range rewriteRegex {
+		if replacer := captureTokens(k, rawURI); replacer != nil {
+			url, err := req.URL.Parse(replacer.Replace(v))
+			if err != nil {
+				return err
+			}
+			req.URL = url
+
+			return nil // rewrite only once
+		}
+	}
+	return nil
+}
+
+// DefaultSkipper returns false which processes the middleware.
+func DefaultSkipper(echo.Context) bool {
+	return false
+}