Adding an address-search component using the OS Places API

[jessicamcinchak]

Idea:
An <os-address-search ... /> web component that would fetch addresses from the OS Places API and render html input(s) following this Gov.UK accessible autocomplete example.

While we currently use the /postcode OS Places endpoint, we could switch to using the /polygon endpoint to offer a single line address search (docs here). Our polygon would come from the /entitiy search of the Digital Land API (beta docs here), which provides the boundary of each local authority. Then we can fetch all addresses in that local authority from OS Places to populate the autocomplete selection list.

Essentially this would be a small shift to starting thinking of this repo as less map-centric, but rather a small library of web components for working with UK address data and Ordnance Survey products.

What it helps solve in the short term:

• Address accessibliity feedback around the FindProperty component (custom combo box input can't be navigated by all assistive devices, lack of proper html markup, lack of useful error messages, etc)
• Moving to the OS Places /polygon endpoint re-introduces the local authority validation that we previously did via GSS code, which is important to partners to ensure applications are submitted to the proper service
• Planx components don't need to manage Ordnance Survey requests / logic directly, they'll just render this web component, pass props (eg local authority name/planx "team"?), and provide an API key. Helps us eliminate some complexity and delete more code as we work towards the open sourcing the Editor milestone ✂️
• It's fun & speedy to work in this repo 😈

Longer term use cases / benefits:

• We know we want to move a single address search in the future anyways, this gets us there sooner and offers a lot of flexibility, as we can still always parse the OS address results into multiple autocomplete input fields if desired
• We could adapt/re-use in the AddressInput component for finding/entering addresses in the UK
• We could adapt/re-use for geocoding in the map web component

Possible challenges?:

• Maintaining smooth "go back" behavior as FindProperty currently does
• Integrating another web component into our React app. We know there's currently some bugs (eg here): if the bug originates with OpenLayers then it wouldn't effect this component, but if it comes from Lit, then we have to figure that out longer term to support any web component (maybe using @lit-labs/react library, which helps simplify event listeners too). Lots more to learn & understand here personally
• Gov.UK's accessible-autocomplete repo behind the example recommended by the accessiblilty auditors hasn't had commit activity in > 1.5 years and there a number of outstanding issues pointing out failures/incompatabilities with newer versions of assistive technologies
  • Alternatively, Gov.UK React components only offers input & select, but doesn't do autocomplete specifically. If we're doing a single line address, the 'search' component might be suitable?

Thoughts? Any other concerns?

[jessicamcinchak]

Dev call notes:

• How expensive is addresses-in-polygon queries via OS? Key/value cloudflare thing for caching?
• Register of scotland accessible example with postcode then address on next screen: https://scotlis.ros.gov.uk/
• Mock it up & test next!

[jessicamcinchak]

#93