Merge branch 'hotfix/#6880-form-element-can-be-added-to-a-fieldset'

Close #6880
Close #6518
Close #6263
[Http] Add body support for DELETE/OPTIONS request
#6492 - simplified HTTP method name checks, removed duplicate/redundant `elseif` statements
#6492 - using `in_array()` instead of large boolean expression
Merge branch 'hotfix/#6492-support-delete-post-request-body' into develop

Close #6492
Forward port #6492