[Bug] PostgreSQL support

[bivashy]

When plugin enables with existing auth table, it will throw this exception:

02:04:34 [SEVERE] java.sql.SQLException: SQL statement failed: CREATE SEQUENCE "auth_links_id_seq"
02:04:34 [SEVERE]     at com.bivashy.auth.lib.com.j256.ormlite.table.TableUtils.doStatements(TableUtils.java:395)
02:04:34 [SEVERE]     at com.bivashy.auth.lib.com.j256.ormlite.table.TableUtils.doCreateTable(TableUtils.java:371)
02:04:34 [SEVERE]     at com.bivashy.auth.lib.com.j256.ormlite.table.TableUtils.doCreateTable(TableUtils.java:356)
02:04:34 [SEVERE]     at com.bivashy.auth.lib.com.j256.ormlite.table.TableUtils.createTableIfNotExists(TableUtils.java:99)
02:04:34 [SEVERE]     at me.mastercapexd.auth.database.dao.AccountLinkDao.<init>(AccountLinkDao.java:36)
02:04:34 [SEVERE]     at me.mastercapexd.auth.database.DatabaseHelper.lambda$new$0(DatabaseHelper.java:59)
02:04:34 [SEVERE]     at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
02:04:34 [SEVERE]     at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
02:04:34 [SEVERE]     at java.base/java.lang.Thread.run(Thread.java:833)
02:04:34 [SEVERE] Caused by: org.postgresql.util.PSQLException: ERROR: relation "auth_links_id_seq" already exists
02:04:34 [SEVERE]     at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2676)
02:04:34 [SEVERE]     at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2366)
02:04:34 [SEVERE]     at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:356)
02:04:34 [SEVERE]     at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:496)
02:04:34 [SEVERE]     at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:413)
02:04:34 [SEVERE]     at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:190)
02:04:34 [SEVERE]     at org.postgresql.jdbc.PgPreparedStatement.execute(PgPreparedStatement.java:177)
02:04:34 [SEVERE]     at com.bivashy.auth.lib.com.j256.ormlite.jdbc.JdbcCompiledStatement.runExecute(JdbcCompiledStatement.java:73)
02:04:34 [SEVERE]     at com.bivashy.auth.lib.com.j256.ormlite.table.TableUtils.doStatements(TableUtils.java:389)
02:04:34 [SEVERE]     ... 8 more

As we can see in stack trace, this is occurred because of ORMLite issue (j256/ormlite-core#20)

[bivashy]

I think we can just use IdentityPostgresDatabaseType from j256/ormlite-core#20 (comment)

I've tested, and it seems like this solves issue.