Pre-filtered search blocks

Problem/Motivation

We've got a use case where we want to have different search blocks for different parts of the site, effectively scoping them for specific areas. It would be ideal we could configure the blocks so that searches run through these instances pre-apply filters that are specified in block config, adding them to the search query.

Steps to reproduce

N/A

Proposed resolution

Implement optional configuration on \Drupal\funnelback\Plugin\Block\SearchBlock to add optional pre-filters to queries.

Remaining tasks

• Add pre-filtering capability to search form
• Make block configurable
• Add pre-filter configuration
• Send config to search form
• Implement tests

User interface changes

Block configuration form to set pre-filters.

API changes

Probably none, but depends on how Funnelback search service is implemented.

Data model changes

Search Block will have schema added to allow configuration.