Configure Docker host in build plugins

This commit adds the ability to configure the Maven and Gradle
plugins to use a remote Docker daemon using build file
configuration, as an alternative to setting environment variables
to specify remote host connection details.

Fixes gh-23400

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/asciidoc/packaging-oci-image.adoc

@@ -34,6 +34,24 @@ The following table shows the environment variables and their values:
 
 On Linux and macOS, these environment variables can be set using the command `eval $(minikube docker-env)` after minikube has been started.
 
+Docker daemon connection information can also be provided using `docker` properties in the plugin configuration.
+The following table summarizes the available properties:
+
+|===
+| Property | Description
+
+| `host`
+| URL containing the host and port for the Docker daemon - e.g. `tcp://192.168.99.100:2376`
+
+| `tlsVerify`
+| Enable secure HTTPS protocol when set to `true` (optional)
+
+| `certPath`
+| Path to certificate and key files for HTTPS (required if `tlsVerify` is `true`, ignored otherwise)
+|===
+
+For more details, see also <<build-image-example-docker,examples>>.
+
 
 
 [[build-image-docker-registry]]
@@ -220,7 +238,21 @@ The image name can be specified on the command line as well, as shown in this ex
 
 [[build-image-example-docker]]
 ==== Docker Configuration
-If the builder or run image are stored in a private Docker registry that supports user authentication, authentication details can be provided as shown in the following example:
+If you need the plugin to communicate with the Docker daemon using a remote connection instead of the default local connection, the connection details can be provided using `docker` properties as shown in the following example:
+
+[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
+.Groovy
+----
+include::../gradle/packaging/boot-build-image-docker-host.gradle[tags=docker-host]
+----
+
+[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
+.Kotlin
+----
+include::../gradle/packaging/boot-build-image-docker-host.gradle.kts[tags=docker-host]
+----
+
+If the builder or run image are stored in a private Docker registry that supports user authentication, authentication details can be provided using `docker.registry` properties as shown in the following example:
 
 [source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
 .Groovy
@@ -234,7 +266,7 @@ include::../gradle/packaging/boot-build-image-docker-auth-user.gradle[tags=docke
 include::../gradle/packaging/boot-build-image-docker-auth-user.gradle.kts[tags=docker-auth-user]
 ----
 
-If the builder or run image is stored in a private Docker registry that supports token authentication, the token value can be provided as shown in the following example:
+If the builder or run image is stored in a private Docker registry that supports token authentication, the token value can be provided using `docker.registry` as shown in the following example:
 
 [source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
 .Groovy

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/gradle/packaging/boot-build-image-docker-host.gradle

@@ -0,0 +1,18 @@
+plugins {
+	id 'java'
+	id 'org.springframework.boot' version '{gradle-project-version}'
+}
+
+bootJar {
+	mainClassName 'com.example.ExampleApplication'
+}
+
+// tag::docker-host[]
+bootBuildImage {
+	docker {
+		host = "tcp://192.168.99.100:2376"
+		tlsVerify = true
+		certPath = "/home/users/.minikube/certs"
+	}
+}
+// end::docker-host[]

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/gradle/packaging/boot-build-image-docker-host.gradle.kts

@@ -0,0 +1,21 @@
+import org.springframework.boot.gradle.tasks.bundling.BootJar
+import org.springframework.boot.gradle.tasks.bundling.BootBuildImage
+
+plugins {
+	java
+	id("org.springframework.boot") version "{gradle-project-version}"
+}
+
+tasks.getByName<BootJar>("bootJar") {
+	mainClassName = "com.example.ExampleApplication"
+}
+
+// tag::docker-host[]
+tasks.getByName<BootBuildImage>("bootBuildImage") {
+	docker {
+		host = "tcp://192.168.99.100:2376"
+		tlsVerify = true
+		certPath = "/home/users/.minikube/certs"
+	}
+}
+// end::docker-host[]