fix(standard-methods): clarify optional parent fields

[toumorokoshi]

There is currently some inconsistency with the description of parent fields on standard methods, and whether they are required.

Clarifying that they are indeed optional, as the resource may not have a parent.

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[rofrankel]

Approved modulo comments, and feel free to just fix the "and and" typo and merge if the other one isn't also some kind of typo.