Provide a way for teachers to invite external participants (guests)

Covered by phpunit and behat tests (the mock server needs to be updated). Warning: the mock server should have the following PR ( https://github.com/moodlehq/bigbluebutton_mock/pull/21 ) merged before being able to successfully run the test. Manual test Preparation As an admin go to Site administration / Plugins / Plugin overview Enable the Bigbluebutton Plugin Then go to Site administration / Plugins / BigBlueButton / Experimental features Ensure that Create guest access link for external guests (bigbluebuttonbn_guestaccess_enabled) is checked Tests session started and approval Setup As an editing teacher or an admin in a course C1, create a new BigblueButton activity B1 In B1 settings, check the Guest access / Guest allowed in meeting checkbox In B1 settings, check the Guest access /User must be approved by moderators Save and display Join the meeting and wait for it to start In the original Browser's tab, click on the gray "Guest access" and copy URL and password in the "Guest access information" popup dialog Test 1: Meeting started and waiting to enter in the meeting In a new private browser window (out of the current session): Go the URL indicated in the "Guest access information" popup dialog Enter a name Enter the password given in the "Guest access information" popup dialog Click Submit Ensure you see a page asking you to wait until the Admin on the current bigbluebutton would allow you in the meeting Test 2: Wrong password In a new private browser window (out of the current session): Go the URL indicated in the "Guest access information" popup dialog Enter a name Enter a different password Click Submit Ensure you see a message saying "Sorry, the password you entered is not the right password. Please contact the moderator for more information.." under the Password to join the meeting as a guest form field. Test 3: Logged in users In a new private browser window (out of the current session): Log in as any moodle user Go to the URL indicated in the "Guest access information" popup dialog Verify that the username field is already filled with the user's name Verify that the username field is read-only Enter the password given in the "Guest access information" popup dialog Click Submit Ensure you see a page asking you to wait until the Admin on the current bigbluebutton would allow you in the meeting Tests session started without approval Same test as above except that in the setup: Enter the password given in the "Guest access information" popup dialog Test 1: Meeting started and NOT waiting to enter in the meeting In a new private browser window (out of the current session): Go the URL indicated in the "Guest access information" popup dialog Enter a name Enter the password given in the "Guest access information" popup dialog Click Submit Ensure you are allowed in the meeting without the need to be approved by the moderator. Tests session not started As an editing teacher or an admin in a course C1, create a new BigblueButton activity B1 In B1 settings, check the Guest access / Guest allowed in meeting checkbox Save and display DO NOT Join the meeting yet In the original Browser's tab, click on the gray "Guest access" and copy URL and password in the "Guest access information" popup dialog Test 1: Meeting not started In a new private browser window (out of the current session): Go the URL indicated in the "Guest access information" popup dialog Enter a name Enter the password given in the "Guest access information" popup dialog Click Submit Ensure you see a message saying "Sorry, the meeting has not yet started, please try again later."