Closes gh-15334

Closes gh-15333

Closes gh-15332

Closes gh-15331

Closes gh-15330

Closes gh-15329

See gh-15328

See gh-15327

Closes gh-15254

Closes gh-15275

Closes gh-15272

Closes gh-15251

Closes gh-15255

Closes gh-14895

Closes gh-15315

Closes gh-15256

Closes gh-15253

Closes gh-15273

Closes gh-15271

Closes gh-15274

Closes gh-15211

This commit adds `ElasticsearchRestHealthIndicator`, a new
`HealthIndicator` for Elasticsearch, using the Elasticsearch "low level
rest client" provided by the
`"org.elasticsearch.client:elasticsearch-rest-client"` dependency.

Note that Spring Boot will auto-configure both low and high level REST
clients, but since the high level one is using the former, a single
health indicator will cover both cases.

See gh-15211

See gh-15273

* pr/14985:
  Polish contribution
  Allow to disable SSL client authentication on the management port

Closes gh-14985

When server and management are at different ports, and when server
requires TLS client authentication, then there is no simple method to
disable TLS client authentication for management port.

This commit adds an additional "none" option to ssl.client-auth.

Example:

    server.port=8080
    server.ssl.enabled=true
    server.ssl.client-auth=need
    management.server.port=8081
    management.server.ssl.enabled=true
    management.server.ssl.client-auth=none

See gh-14985

Closes gh-15317

Closes gh-15227