automod: add removing of labels from accounts and records

[haileyok]

i haven't tested this yet - and took me a little to understand what we were doing here so might still be a little off - but this should let us remove existing labels from accounts/records

[haileyok]

one thing that might be weird here is if one rule adds a label and then another negates the label, need to think that through as i think it could get wonky with the current logic here in the pr....

early and still not fully caffeinated, but i think i got some decent logic here. imagine a scenario like:

• Rule 1 executes and decides to AddLabel("sexual")
• Rule 2 executes and decides to RemoveLabel("sexual")

Here, we'd keep the sexual label in the new labels to add (assuming it wasn't already added on the account/record).

• Rule 1 executes and decides to RemoveLabel("sexual")
• There is no sexual label on the account/record

Here we'd remove the sexual label from the rmdLabels, since there's no point in negating it.

• Rule 1 executes and decides to RemoveLabel("sexual")
• There is already a negated sexual label on the account/record

Here we'd remove the sexual label from the rmdLabels, since again in negating it.

[bnewbold]

one little typo, but otherwise looks good!

[bnewbold]

Record / Account swapped here (sorry this code is so duplicative)

[haileyok]

oop nice catch ty

[bnewbold]

embarrassing idiomatic golang question: should this be:

rmdLabels := []string{}

specifically b/c it gets len() called on it, and passed to NegateLabelVals below. probably fine/same either way. "is zero/nil of an array of strings same as empty array"

[haileyok]

it would be fine for the len() case. good point though with getting passed to NegateLabelVals. i'm not sure if the api would be happy with a null (or omitted? didnt look closely) value after marshaling, so yea let's just initialize the empty array