Release notes for v2.3.1

This minor release contains some community pull requests along with a few bug fixes and documentation updates.

This release includes no additional data migrations.

Community Contributions

Update of documentation - thanks to Blake Carver and uetuluk.
Enabling the use of subject term type with the MODS exporter - thanks to Lora Woodford.
Additional repository scoping of reports - thanks to Steve Majewski.
Improvements of error handling for no repositories and inability to connect to backend - thanks to Chris Fitzpatrick.
Updates to the Docker setup, exposing solr parameters in the config file, adding backend only option for supervisord and capability for s3 storage for index state files - thanks to Mark Cooper.
Thanks to the Development Prioritization Sub-team for prioritizing ANW-289 and ANW-428 which are included in this release.
Thanks to the Core Committers Group members for reviewing and merging pull requests for this release.

Pull Request #1094 Optional addition of s3 storage for index state
Pull Request #1106 Better handling of error on repository page for a freshly installed instance without any repositories and displays an error page if it cannot connect to the backend
Pull Request #1110 and #1125 Repository scoping of reports
Pull Request #1121 Documentation update - pui_branding_img needs a full path
Pull Request #1126 Add backend only option for supervisord
Pull Request #1127 Add lang attribute to html tag for staff interface
Pull Request #1128 Expose additional Solr params via AppConfig
Pull Request #1130 Releases require mime-types gem for IndexStateS3
Pull Request #1132 Update documentation with correct spaces in YAML example
ANW-428 and Pull Request #1133 Move audit information fields (created_by and last_modified_by) out of keyword search for both public and staff interfaces) and into advanced search selections on staff interface only
ANW-289 and Pull Request #1134 Enabling the use of subject term type with the MODS exporter
Pull Request #1135 Documentation update for repo_code example
Pull Request #1138 and #1139 Update documentation since prefixes are fixed in new versions