9.0.0-beta9

See last link for the details about the following highlights:

• Bump webflo/drupal-finder (#3105). Thanks @webflo
• The sites/all/drush folder is no longer a valid location for alias files
• Remove bastion.md.
• Test with Drupal 8.4.x and 8.5.x. #2980
• Stop setting SERVER globals. Build a Request instead (#3109)
• Added slack channel to support section. (#3112). Thanks @Chi-teck
• Fix #3063. Add example of dynamic alias alter (#3115)
• Fix categorization of the generate commands.
• Stop using further() in sql commands. Use @bootstrap max instead. (#3135)
• #3123 - Global D8 container is not available during container rebuild. Thanks @kevin-dutra
• Make it possible to set the uri option in drush.yml. Fixes #3121. Thanks @eiriksm
• Plan for the future (see #3130): Allow for phpunit 5.x. (#3139)
• Fix the batch finished callback for 'updatedb' command. (#3144). Thanks @claudiu-cristea
• Fix #3133. Add site alias generator. (#3142)
• Misc bug fixes
• Changes since 9.0.0-beta8.