Added
- Traffic Ops: added a feature so that the user can specify `maxRequestHeaderBytes` on a per delivery service basis
- Traffic Router: log warnings when requests to Traffic Monitor return a 503 status code
- [5344](https://github.com/apache/trafficcontrol/issues/5344) - Add a page that addresses migrating from Traffic Ops API v1 for each endpoint
- [5296](https://github.com/apache/trafficcontrol/issues/5296) - Fixed a bug where users couldn't update any regex in Traffic Ops/ Traffic Portal
- Added API endpoints for ACME accounts
- Traffic Ops: Added validation to ensure that the cachegroups of a delivery services' assigned ORG servers are present in the topology
- Traffic Ops: Added validation to ensure that the `weight` parameter of `parent.config` is a float
- Traffic Ops Client: New Login function with more options, including falling back to previous minor versions. See traffic_ops/v3-client documentation for details.
- Added license files to the RPMs
Fixed
- [5288](https://github.com/apache/trafficcontrol/issues/5288) - Fixed the ability to create and update a server with MTU value >= 1280.
- [1624](https://github.com/apache/trafficcontrol/issues/1624) - Fixed ORT to reload Traffic Server if LUA scripts are added or changed.
- [5445](https://github.com/apache/trafficcontrol/issues/5445) - When updating a registered user, ignore updates on registration_sent field.
- [5335](https://github.com/apache/trafficcontrol/issues/5335) - Don't create a change log entry if the delivery service primary origin hasn't changed
- [5333](https://github.com/apache/trafficcontrol/issues/5333) - Don't create a change log entry for any delivery service consistent hash query params updates
- [5341](https://github.com/apache/trafficcontrol/issues/5341) - For a DS with existing SSLKeys, fixed HTTP status code from 403 to 400 when updating CDN and Routing Name (in TO) and made CDN and Routing Name fields immutable (in TP).
- [5192](https://github.com/apache/trafficcontrol/issues/5192) - Fixed TO log warnings when generating snapshots for topology-based delivery services.
- [5284](https://github.com/apache/trafficcontrol/issues/5284) - Fixed error message when creating a server with non-existent profile
- [5287](https://github.com/apache/trafficcontrol/issues/5287) - Fixed error message when creating a Cache Group with no typeId
- [5382](https://github.com/apache/trafficcontrol/issues/5382) - Fixed API documentation and TP helptext for "Max DNS Answers" field with respect to DNS, HTTP, Steering Delivery Service
- [5396](https://github.com/apache/trafficcontrol/issues/5396) - Return the correct error type if user tries to update the root tenant
- [5378](https://github.com/apache/trafficcontrol/issues/5378) - Updating a non existent DS should return a 404, instead of a 500
- Fixed a potential Traffic Router race condition that could cause erroneous 503s for CLIENT_STEERING delivery services when loading new steering changes
- [5195](https://github.com/apache/trafficcontrol/issues/5195) - Correctly show CDN ID in Changelog during Snap
- [5438](https://github.com/apache/trafficcontrol/issues/5438) - Correctly specify nodejs version requirements in traffic_portal.spec
- Fixed Traffic Router logging unnecessary warnings for IPv6-only caches
- [5294](https://github.com/apache/trafficcontrol/issues/5294) - TP ag grid tables now properly persist column filters on page refresh.
- [5295](https://github.com/apache/trafficcontrol/issues/5295) - TP types/servers table now clears all filters instead of just column filters
- [5407](https://github.com/apache/trafficcontrol/issues/5407) - Make sure that you cannot add two servers with identical content
- [2881](https://github.com/apache/trafficcontrol/issues/2881) - Some API endpoints have incorrect Content-Types
- [5311](https://github.com/apache/trafficcontrol/issues/5311) - Better TO log messages when failures calling TM CacheStats
- [5364](https://github.com/apache/trafficcontrol/issues/5364) - Cascade server deletes to delete corresponding IP addresses and interfaces
- [5390](https://github.com/apache/trafficcontrol/issues/5390) - Improve the way TO deals with delivery service server assignments
- [5339](https://github.com/apache/trafficcontrol/issues/5339) - Ensure Changelog entries for SSL key changes
- [5461](https://github.com/apache/trafficcontrol/issues/5461) - Fixed steering endpoint to be ordered consistently
- [5395](https://github.com/apache/trafficcontrol/issues/5395) - Added validation to prevent changing the Type any Cache Group that is in use by a Topology
- Fixed an issue with 2020082700000000_server_id_primary_key.sql trying to create multiple primary keys when there are multiple schemas.
- Fix for public schema in 2020062923101648_add_deleted_tables.sql
- Fix for config gen missing max_origin_connections on mids in certain scenarios
- [5642](https://github.com/apache/trafficcontrol/issues/5642) - Fixed ORT to fall back to previous minor Traffic Ops versions, allowing ORT to be upgraded before Traffic Ops when the minor has changed.
- Moved move_lets_encrypt_to_acme.sql, add_max_request_header_size_delivery_service.sql, and server_interface_ip_address_cascade.sql past last migration in 5.0.0
- [5505](https://github.com/apache/trafficcontrol/issues/5505) - Make `parent_reval_pending` for servers in a Flexible Topology CDN-specific on `GET /servers/{name}/update_status`
- [5317](https://github.com/apache/trafficcontrol/issues/5317) - Clicking IP addresses in the servers table no longer navigates to server details page.
- 5554 - TM UI overflows screen width and hides table data
Changed
- [5553](https://github.com/apache/trafficcontrol/pull/5553) - Removing Tomcat specific build requirement
- Refactored the Traffic Ops Go client internals so that all public methods have a consistent behavior/implementation
- Pinned external actions used by Documentation Build and TR Unit Tests workflows to commit SHA-1 and the Docker image used by the Weasel workflow to a SHA-256 digest
- Set Traffic Router to only accept TLSv1.1 and TLSv1.2 protocols in server.xml
- Updated Apache Tomcat from 8.5.57 to 8.5.63
- Updated Apache Tomcat Native from 1.2.16 to 1.2.23
- Traffic Portal: [5394](https://github.com/apache/trafficcontrol/issues/5394) - Converts the tenant table to a tenant tree for usability
- Traffic Portal: upgraded delivery service UI tables to use more powerful/performant ag-grid component