User agent stop list

Problem/Motivation

REcombee tracking will be triggered whenever a page is requested an Javascript is run on that page. This can potentially cause problems with repeated or automated process (webcrawlers, testing) where the site is regularly exercised. If the tracking code is run, a new client id will be generated and logged into teh Recombee database. This will lead to a lot of new clients with only one interaction.

This has a number of downsides:
* Database is diluted.
* User quota will be exceeded, pushing you into a higher plan.

Steps to reproduce

Repeately request pages on the site, running JS with a new context.

Proposed resolution

Add a "Tracker stoplist" text field which can hold a regex of UA strings to match on.

eg. /bot|headless/

See https://stackoverflow.com/questions/116819/regular-expression-to-exclude...

Remaining tasks

Add a new field to the tracker block.
Wrap the tracking JS in a conditional.

User interface changes

New field.

API changes

None.

Data model changes

The regex string needs to be passed through to the tracker JS, probably in Drupal settings.