New Features

• client: implement support for "unix" resolver scheme (#3890)
• rds: allow case_insensitive path matching (#3997)
• credentials/insecure: implement insecure credentials. (#3964)
• lrs: handle multiple clusters in LRS stream (#3935)

Performance Improvements

• encoding/proto: simplify & optimize proto codec (#3958)

Bug Fixes

• internal/transport: fix a bug causing -bin metadata to be incorrectly encoded (#3985)
  • Special Thanks: @dntj
• grpclb: consider IDLE SubConns as connecting (#4031)
• grpclb: send custom user-agent (#4011)
• client: use "localhost:port" as authority if target is ":port" (#4017)
• credentials: fix PerRPCCredentials w/RequireTransportSecurity and security levels (#3995)

Documentation

• Documentation: fix outgoing metadata example code (#3979)
  • Special Thanks: @aaronjheng
• Remove experimental comment from client interceptors (#3948)
  • Special Thanks: @hypnoglow
• Documentation: update keepalive.md to add why (#3993)