docs: mention `id` field in `1-abstract-dto.rst` #4583

Job	Run time
mypy	1m 1s
pyright	1m 3s
slotscheck	25s
Test server integration (uvicorn<0.27.0)	43s
Test Minimal Application with Base Dependencies	13s
Test server integration (uvicorn>=0.27.0)	37s
validate	19s
Test Minimal Pydantic 1 application	17s
test-platform-compat	0s
test (3.10) / test	1m 48s
test (3.11) / test	1m 46s
test (3.12) / test	2m 58s
test (3.8) / test	2m 47s
test (3.9) / test	1m 56s
build-docs	2m 18s
codeql	1m 49s
upload-test-coverage	14s
sonar	51s
	21m 5s

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