Move `UpdateUser` methods into `after_update` callbacks on `User` #1931

Job	Run time
test-ruby-matrix (4, 0)	2m 39s
test-ruby-matrix (4, 1)	2m 35s
test-ruby-matrix (4, 2)	3m 18s
test-ruby-matrix (4, 3)	2m 21s
CodeQL SAST scan / Analyze	1m 30s
Dependency Review scan / dependency-review-push	0s
Dependency Review scan / dependency-review-pr	3s
Lint JavaScript / Run Standardx	10s
Lint Ruby / Run RuboCop	13s
Lint SCSS / Run Stylelint	9s
Security Analysis / Run Brakeman	12s
SNYK security analysis / sast	15s
SNYK security analysis / sca	10s
Test JavaScript / Run Jasmine	48s
Test Ruby	1s
	14m 24s

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