Standalone tool for initializing of hawkBit Database (#2369)

Signed-off-by: Avgustin Marinov <Avgustin.Marinov@bosch.com>

hawkbit-repository/hawkbit-repository-jpa-init/README.md

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+# hawkBit JPA Initializer & Migrator
+
+A standalone tool for validating and migrating the database to the current hawkBit schema. It is used to validate, initialize or migrate the database to the current hawkBit schema. 
+
+## Configuration
+Could be configured with _hawkbit.db.\<key\>_ or <spring.database.\<key\>_ environment or system properties, with keys:
+* **mode** - migrate or validate (default)
+* **url** - database url
+* **username** - database user - shall have the necessary permissions
+* **password** - database user's password
+* **sql-migration-suffixes** - flyway 'sqlMigrationSuffixes' if not the default ones (<upper case database (mariadb -> mysql)>.sql)
+
+Where:
+1. Environment properties takes precedence over the system properties
+2. The _hawkbit.db.\<key\>_ properties take precedence over the _spring.database.\<key\>_ properties
+
+There are two modes:
+* **migrate** - migrate the database, only when started with parameter with key mode (environment or system property)
+* **validate** - validate the database, default, only validates db and throws org.flywaydb.core.api.exception.FlywayValidateException if not in sync
+
+**Note**: could also be configured using default flyway env properties
+
+## Usage
+The module builds executable jar with all dependencies - _hawkbit-repository-jpa-init-\<revision\>-exec.jar_. It could be configured with environment properties and run as an executable jar:
+```shell
+# sets the mode - default if validate
+export hawkbit_db_mode=migrate 
+# sets the database url - default is local h2
+export hawkbit_db_url=jdbc:mariadb://localhost:3306/hawkbit
+# sets the database user - default is h2 default root - sa
+export hawkbit_db_username=root
+# sets the database user's password - default is empty
+#export hawkbit_db_password=
+
+# run executable jar
+java -jar target/hawkbit-repository-jpa-init-0-SNAPSHOT-exec.jar
+```
+
+It could also be configured using system properties and run as a java main class:
+```shell
+java -classpath target/hawkbit-repository-jpa-init-0-SNAPSHOT-exec.jar \
+  -Dhawkbit.db.mode=migrate \
+  -Dhawkbit.db.url=jdbc:mariadb://localhost:3306/hawkbit \
+  -Dhawkbit.db.username=root \
+  -Dhawkbit.db.password= \
+  org.eclipse.hawkbit.repository.jpa.init.HawkbitFlywayDbInit
+```
+
+## Purpose and usecases
+If you want to do db management separately from the running services - i.e. not in mgmt-server or monolith (for instance) servers but only occasionally and on real updates, or you like to validate a database according to a hawkbit db schema version you could:
+1. set spring.flyway.enabled=false in the hawkbit services (or do not pack the hawkbit-repository-jpa-flyway module into the hawkbit services)
+2. use the tool to do the db management (e.g. in some pipelines)