[4] After authentication failure, return to the login page with a GET request

[PhilETaylor]

Pull Request for Issue # #32895

Summary of Changes

After attempting to login with invalid credentials, you are not redirected back to the login page, so pressing refresh actually attempts to send the POST request a second time.

Administrator login form doesn't follow Post/Redirect/Get pattern

(also a quick typo fix in comment)

Testing Instructions

Attempt to login to Joomla 4 with invalid credentials.
Inspect the requests/responses with browser inspector tools

Actual result BEFORE applying this Pull Request

Request: POST of invalid credentials
Response: HTML with error message, if you refresh the page the browser asks to resend the form

Expected result AFTER applying this Pull Request

Request: POST of invalid credentials
Response: 303 Other redirect to /administrator/index.php
browser follows redirect (not always shown in the inspector on some browsers, look hard, it fooled me too)
Response: GET /administrator/index.php, if you refresh the page the browser just performs a refresh (GET) and validation message is missing as its already displayed

Documentation Changes Required

none

[toivo]

I have tested this item ✅ successfully on 5fe0333

Tested successfully in Beta8-dev updated to 29 March in Windows 10 running Wampserver 3.2.4 and PHP 8.0.2.

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/32897.}

[ceford]

I have tested this item ✅ successfully on 5fe0333

I used the Firefox live headers and selected a un/pw not for my test site - surprised to see the pw in plain text in the record! A sobering lesson!

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/32897.}

[Quy]

RTC

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/32897.}