Move `UpdateUser` methods into `after_update` callbacks on `User` #1758

Job	Run time
test-ruby-matrix (4, 0)	2m 37s
test-ruby-matrix (4, 1)	3m 31s
test-ruby-matrix (4, 2)	2m 23s
test-ruby-matrix (4, 3)	2m 24s
CodeQL SAST scan / Analyze	1m 30s
Dependency Review scan / dependency-review-pr	4s
Dependency Review scan / dependency-review-push	0s
Lint JavaScript / Run Standardx	13s
Lint Ruby / Run RuboCop	13s
Lint SCSS / Run Stylelint	24s
Security Analysis / Run Brakeman	13s
Test JavaScript / Run Jasmine	53s
Test Ruby	0s
	14m 25s

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