V5.6.1: Bug fixes, cleanup and deprecations

Changed

• Add rel="nofollow" to the sorting links in the list view (#3311)
• Make injected services in EventRegistrationController protected (#3297)
• Make getFirstOrganizer() non-nullable (#3254)

Deprecated

• Deprecate AbstractTimeSpam::getEndDate() (#3310)
• Deprecate LegacySpeaker::isHidden() (#3310)
• Deprecate the RegistrationManager::SEND_*_EMAIL constants (#3310)
• Deprecate the EmailBuilder class (#3310)
• Deprecate RegistrationManager::isUserRegisteredMessage() (#3310)
• Deprecate CSV-exporting the user group for registrations (#3310)
• Deprecate the SingleViewLinkBuilder class (#3310)
• Deprecate the CSV export of events (#3310)
• Deprecate $isFileName parameter in TemplateHelper::getConfValueString()(#3310)
  (#3310)

Removed

• Drop obsolete TypoScript option (#3294)
• Drop unused AbstractPlugin code from TemplateHelper
  (#3237, #3238, #3240, #3241, #3242, #3243, #3245, #3246, #3250, #3251, #3253,
  #3255, #3256, #3258, #3260, #3261, #3263, #3264, #3265, #3266, #3268, #3269,
  #3270, #3273, #3274)
• Drop redundant type casts (#3229, #3267)
• Drop redundant null coalescing operators (#3228)
• Remove dead code from TemplateHelper (#3220, #3221, #3222, #3223, #3224)

Fixed

• Avoid using the deprecated Extbase models (#3322)
• Mock controller methods in a TYPO3-version-specific way (#3321)
• Use the correct queue for flash messages in the BE module (#3305)
• Work around problems with the back button in the BE module search (#3293)
• Drop duplicate labels (#3285)
• Fix deprecation warning when rendering rich text (#3275)
• Fix type errors in TemplateHelper (#3232)
• Avoid using the short ternary operator (#3230)
• Always use strict comparisons in TemplateHelper (#3215, #3225)
• Avoid usage of empty in TemplateHelper (#3214)
• Always call htmlspecialchars with flags (#3209)
• Improve some type annotations
  (#3205, #3206, #3211, #3217, #3218, #3219, #3227, #3234, #3236, #3247, #3252)