Database connection string "pg_opt" and "database" config options should not be used both

[kuvaldini]

Please remove deprecated "pg_opt" from documentation.
Please check this is the only place.

Please also address #898

@LiraLemur Please consider to update example/config.sample and force Sphinx to load code sample from source-tree rather than copy contents to doc!

[LiraLemur]

@kuvaldini the database too, right? The whole block? Or only the pg_opt?

[kuvaldini]

"Database" is actual config, pgopt is old and deprecated.

[kuvaldini]

@LiraLemur the best way is to load content from file example/config.sample'

[LiraLemur]

@kuvaldini it's possible for the general example but there's also a description part anyway, which is simply impossible to load and it's important.

[kuvaldini]

The file should be loaded, description should forget about pg_opt and use corresponding config keys under "database" config tree

[LiraLemur]

I will make it load the file but we need to load it from the default branch which is main atm and there there is no metrics yet.
Just FYI @kuvaldini

Should be fine when it's merged into the main though

[kuvaldini]

For branch support/1.2.x or any other please use config.sample exactly from the same branch. NOT from main. That is important.

This does not touch anything about metrics.