Mixin: detroit_authority is broken

[rhetr]

affected spiders

• det_brownfield_redevelopment_authority.py
• det_downtown_development_authority.py
• det_economic_development_corporation.py
• det_eight_mile_woodward_corridor_improvement_authority.py
• det_local_development_finance_authority.py
• det_neighborhood_development_corporation.py
• det_next_michigan_development_corporation.py

proposed solution

short term: scrape the embedded yoast schema graph to graph the information
long term: create a new mixin using the wordpress events calendar API as mentioned in #22

status

i created a branch in my fork and updated the scraper to parse the yoast schema graph; however, the tests are failing. I'm unsure if it is imperative to fix the tests since we plan to overhaul the mixin in the near future anyway.

it's also unclear to me the exact purpose of _parse_prev_meetings() but it doesn't seem to be broken so i have not modified it.