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>

api/v4/source/remoteclusters.yaml

@@ -81,7 +81,6 @@
               type: object
               required:
                 - name
-                - password
               properties:
                 name:
                   type: string
@@ -89,7 +88,10 @@
                   type: string
                 password:
                   type: string
-                  description: The password to use in the invite code.
+                  description: |
+                    The password to use in the invite code. If empty,
+                    the server will generate one and it will be part
+                    of the response
       responses:
         "201":
           description: Remote cluster creation successful
@@ -103,6 +105,11 @@
                   invite:
                     type: string
                     description: The encrypted invite for the newly created remote cluster
+                  password:
+                    type: string
+                    description: |
+                      The password generated by the server if none was
+                      sent on the create request
         "401":
           $ref: "#/components/responses/Unauthorized"
         "403":