bugfix: avoid generating an invalid ID attribute in SAML's AuthenRequest element

Google hosted domain support

Avoid generating an identifer which starts with a number because it may be used as a SAML's ID attribute

examples: document explicit flow in example config

Update using-dex.md

Update using-dex.md

Documentation/github-connector: warn user that GitHub email id should be public.

connector: improve error message for callback URL mismatch

Documentation/ldap-connector.md: Warn about LDAP connector's bindPW restriction.

server: fix localhost redirect validation for public clients

connector/ldap: correct a comment.

connector/ldap: check for blank passwords and return error.

cmd/dex/serve: add local connector directly to static connectors in storage

server/api: return empty list of refresh tokens if user does not have any

server: account for dynamically changing connector object in storage.

README.md: reorganize README

* Highlights that dex is NOT a user-management system.
* Highlights ID Tokens as dex's primary feature.
* General cleanup.

Update kubernetes.md

fixed typo

Documentation: add a doc describing how to use dex

*: update maintainers