hawkBit rest docs (management & DDI API) (#688)

* hawkBit REST docs.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

* Fiy gitignore.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

* Add to website.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

* Switch to generated docs.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

* Fix typos.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

* Review findings.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

* Otimizations.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

* Revert accidental checkin.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

* Add security link.

.gitignore

@@ -5,6 +5,7 @@ tmp
 .settings
 .classpath
 target
+!hawkbit-rest/hawkbit-mgmt-api/src/main/java/org/eclipse/hawkbit/mgmt/json/model/target
 .allure
 .vscode
 .springbeans