Added missing la_fld_ExtraHTTPHeaders phrase.

I've added # (new) apply the patch from the D524, unless it's already committed line, that should fix the problem. Please retest.

2.2 - this part of test plan is excessive

Added code to support changes from the D466.

1. resubmit from the 5.3.x branch, because an associated Jira task is for the 5.3.x branch as well.
2. (test plan only tests 50% of changed code) improve test plan by checking, that request header logging still works, when HttpQuery is present

In D519#10607, @erik wrote:

Part 2 - "confirm, that you're seeing an Admin Console" - no, adding test code to OnLogin prevents from login to the adm.console.

Applying the Boyscout Rule principe.

In D518#10578, @erik wrote:

Today I have z-index; 0; in DIV Can't provide screenshot without -index today.

In D518#10573, @erik wrote:

Added reference to the used code origins.

Update test plan to cover requested changes as well.

In D513#10483, @erik wrote:

Part 3.1.1 login to the Admin Console by accessing it on the sd1.test.domain.com domain over http:// protocol - FAILED, after login attempt - redirect to the login page. SUCCESS after cookies deleted (beyond test plan)
Part 3.1.12 confirm, that orange buttons for editing page/content blocks are now shown - NOT STABLE. At first attempt - no orange buttons. Then I logged in from main domain, set Default theme as primary theme, checked that orange buttons shown, restored Advanced theme as primary theme, then tried again login to sd1 domain, failed, cleared cookies, login to sd1 admin - and only then orange buttons shown

In D511#10453, @erik wrote:

Part 3.2 go to the Configuration → Website → Advanced section - FAILED, can't. login, redirects to login screen. Logged in only after all current site cookies deleted before login.

Added some explanatory comments.

In D513#10467, @erik wrote:

Part 3.1.7 confirm that [SD ID: 1] is added in the current page blur bar (the 1 is site domain ID) - NO, [SD ID: ] is added. And this is right, because at Preparations 10 "add 1st site domain with: Domain Name=sd1-http.test.domain.com", not sd1.test.domain.com
Part 3.1.9 confirm, that you'll see [Site Domain ID: 1] text (the 1 is site domain ID) - NO I see [Site Domain ID: 0]

Excluded "site_domain_eh.php" with no changes from the Differential Revision.

Restored Browse Mode support when Front-End and Admin Console are using different SSL domains.

Discovered a bug where Front-End can’t be opened in a Browse Mode if SSL is being used and Front-End and Admin Console are using different SSL domains.

Updated test plan. Please retest.

In D511#10419, @erik wrote:

All tested, there is list of possible differences from test plan expectations.

Part 2.7 confirm you stayed on the admin1-https.test.domain.com domain and http:// protocol - NO, STAYED ON same domain/protocol test.domain.com

Ensure new identical field order in both unit config and database table.

1. extract "\ChangeLogHelper::getUserFields" from the "\ChangeLogHelper::getAddFields" for easier customization
2. change cache key of the \ChangeLogHelper::getAddFields method to include also session_id

Rebase on top of D504.