Resolve "Anmeldung am Servicekonto & Token Erstellung"

Closes #3 (closed)

src/main/java/de/ozgcloud/nachrichten/postfach/osiv2/config/OsiPostfachProperties.java

+package de.ozgcloud.nachrichten.postfach.osiv2.config;
+
+import jakarta.annotation.Nullable;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.context.annotation.Configuration;
+
+import lombok.Getter;
+import lombok.Setter;
+
+@Getter
+@Setter
+@Configuration
+@ConfigurationProperties(prefix = OsiPostfachProperties.PREFIX)
+public class OsiPostfachProperties {
+
+	static final String PREFIX = "ozgcloud.osiv2-postfach";
+
+	private boolean enabled;
+
+	@Getter
+	@Setter
+	@Configuration
+	@ConfigurationProperties(prefix = ApiConfiguration.PREFIX)
+	static class ApiConfiguration {
+		static final String PREFIX = OsiPostfachProperties.PREFIX + ".api";
+
+		private String resource;
+		private String url;
+		private String tenant;
+		private String nameIdentifier;
+	}
+
+	/**
+	 * HTTP proxy configuration. To use basic HTTP authentication configure username and password. (See <a
+	 * href="https://github.com/reactor/reactor-netty/blob/3b74fcf2f5b2bdd129636e9c55608f0187ef7bd4/reactor-netty-core/src/main/java/reactor/netty/transport/ProxyProvider.java#L142">ProxyProvider</a>)
+	 */
+	@Getter
+	@Setter
+	@Configuration
+	@ConfigurationProperties(prefix = ProxyConfiguration.PREFIX)
+	static class ProxyConfiguration {
+		static final String PREFIX = OsiPostfachProperties.PREFIX + ".http-proxy";
+
+		private boolean enabled;
+
+		private String host;
+		private Integer port;
+
+		@Nullable
+		private String username = null;
+		@Nullable
+		private String password = null;
+	}
+}