chore: fix SQL queries with double quoted field names and unbreak integration tests.

Configure H2 to not convert unquoted identifiers to an upper case by default.

See for details:
- https://www.h2database.com/javadoc/org/h2/engine/DbSettings.html#DATABASE_TO_UPPER
- https://stackoverflow.com/questions/10789994/make-h2-treat-quoted-name-and-unquoted-name-as-the-same

Should be in 74734a8 commit.

Relate to #1326

Author: php-coder

src/main/resources/application-test.properties

@@ -1,6 +1,6 @@
 spring.profiles: test
 
-spring.datasource.url: jdbc:h2:mem:mystamps;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=false
+spring.datasource.url: jdbc:h2:mem:mystamps;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=false;DATABASE_TO_UPPER=false
 spring.datasource.username: sa
 spring.datasource.password:
 spring.datasource.driver-class-name: org.h2.Driver