Allows creating new remote clusters without providing a password (#27864)

* Allows creating new remote clusters without providing a password

If the endpoint receives a request with no password, it will generate
one internally and return it in the response, so the frotend can show
it to the user.

* Use a random string instead of a UUID for the generated password

* Update function name to avoid CString reference and adds assertion

* Update server/channels/utils/textgeneration.go

Co-authored-by: Eva Sarafianou <eva.sarafianou@gmail.com>

* Extends the charset

---------

Co-authored-by: Eva Sarafianou <eva.sarafianou@gmail.com>

server/channels/utils/textgeneration.go

@@ -4,7 +4,9 @@
 package utils
 
 import (
-	"math/rand"
+	crand "crypto/rand"
+	"math/big"
+	mrand "math/rand"
 	"strings"
 )
 
@@ -468,11 +470,23 @@ Up to and hey without pill that this squid alas brusque on inventoried and sprea
 func RandString(l int, charset string) string {
 	ret := make([]byte, l)
 	for i := 0; i < l; i++ {
-		ret[i] = charset[rand.Intn(len(charset))]
+		ret[i] = charset[mrand.Intn(len(charset))]
 	}
 	return string(ret)
 }
 
+func SecureRandString(n int) string {
+	charset := "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!@#$%&*0123456789"
+
+	var str strings.Builder
+	for i := 0; i < n; i++ {
+		num, _ := crand.Int(crand.Reader, big.NewInt(int64(len(charset))))
+		str.WriteString(string(charset[num.Int64()]))
+	}
+
+	return str.String()
+}
+
 // func RandomEmail(length Range, charset string) string {
 // 	emaillen := RandIntFromRange(length)
 // 	username := RandString(emaillen, charset)
@@ -517,7 +531,7 @@ func RandomText(length Range, hashtags Range, mentions Range, users []string) st
 
 	// Shuffle the words
 	for i := range words {
-		j := rand.Intn(i + 1)
+		j := mrand.Intn(i + 1)
 		words[i], words[j] = words[j], words[i]
 	}