Add $0 bill output for PINs with an EAV less than $150

[kyrasturgill]

This PR adds an exception to the tax_bill() function, defaulting the tax bill amount to zero when a PIN's final EAV is less than $150, mirroring the Treasurer which does not send tax bills to PINs with an EAV that is less than $150 and ultimately records the bill as $0. This ensures alignment between the final_tax output of the tax_bill() function and the tax_bill_total field which mirrors the final bill amount from the Treasurer's data.

[jeancochrane]

Thanks so much for the quick turnaround! A couple nits and questions below, but nothing serious.

[jeancochrane]

[Question, non-blocking] Something I should have thought about earlier: Do you know if the Treasurer's $150 limit applies to the pre- or post-exemption EAV? This code will apply it to the pre-exemption EAV, which may lead tax_bill() to miss some $0 bills if the Treasurer's logic actually depends on post-exemption EAV.

[kyrasturgill]

AH I can't believe I didn't think of that! I believe it is post-exemption EAV. I did a test and found that there are PINs with pre-exemption EAV over $150 but a post-exemption under that have tax_bill_total equal to $0.

[kyrasturgill]

This is updated with commit 895fb0f

[jeancochrane]

Good to go!

[kyrasturgill]

Documenting for posterity - I did some QC to ensure the PINs impacted by the change to the function were those we'd expect (taxable EAV < 150). In doing a quick calc of taxable EAV of av_clerk * eq_factor_final - exe_total, I found that farmland (class 239) can return "taxable EAV" > 150 (from the calc, that's not actually the farmland's taxable EAV as farmland is not equalized) but have a zero bill. This is because in the tax_bill() function we have:

dt[class == "239", eav := av] # farmland is taxed on AV, not EAV

So, this update for handling taxable eav < 150 will return $0 bill for farmland with av < 150. Turns out this rule aligns with what shows up in tax_bill_total - for all years, any 239 PIN with an AV < 150 has tax_bill_total equal to 0. So we're good, but wanted to just document in case anyone happens to inquire about how farmland is handled in this situation.