Add a test for installing a plugin

[hhorak]

This will fail until the plugin dir is fixed in the base.cnf file (fix suggested in #235).

[hhorak]

[test]

[phracek]

Test failed:

-----------------------------------------------
Running test run_plugin_test (starting at 2024-04-05 14:32:09+00:00) ... 
-----------------------------------------------
  Testing plugin installation
    Created container 66f8fd9a9e55803a746273b23524e4da95ce81229c1a1199f67ba5f9fa9b839d
  Testing MySQL connection to 10.88.0.174...
    Trying to connect....... OK
  Success!
ERROR 1126 (HY000) at line 1: Can't open shared library '/usr/lib64/mysql/plugin/sql_errlog.so' (errno: 2, cannot open shared object file: No such file or directory)
Test for image 'quay.io/sclorg/mariadb-103-c8s:1' FAILED (exit code: 1)
ERROR 1146 (42S02) at line 1: Table 'mysql.IdonotExist' doesn't exist
grep: /var/lib/mysql/data/sql_errors.log: No such file or directory
Test for image 'quay.io/sclorg/mariadb-103-c8s:1' FAILED (exit code: 2)
Test for image 'quay.io/sclorg/mariadb-103-c8s:1' FAILED (exit code: 2)
Tests finished with EXIT=0

==============================================

But it looks like it needs #235

[hhorak]

[test]

[phracek]

The tests passed, but I have missed the documentation about plugin.

[phracek]

SQL_ERROR_LOG is the plugin or SONAME? I do not follow.
It is not clear to me as a database dummy folk. Is it documented somewhere?

If not, can you please add this to documentation?

[hhorak]

This test only follows what is documented in upstream: https://mariadb.com/kb/en/sql-error-log-plugin/
I don't personally see a need to duplicate upstream documentation here, although I'm not against if somebody volunteers to do it.