Prefer $connect_settings over explicit parameters

[bastelfreak]

This is the outcome of a large refactoring in #1450 and discussions on IRC and slack. We noticed that the behaviour of $connect_settings is currently inconsistent. Sometimes it's preferred over explicity parameters, sometimes not.

Reminder: The idea of $connect_settings is to provide a hash with environment variable to tell puppet to manage a remote database instead of a local instance.

One example is:

puppetlabs-postgresql/manifests/server/grant.pp

Lines 80 to 86 in 93386b4

	if $port {
	$port_override = $port
	} elsif 'PGPORT' in $connect_settings {
	$port_override = undef
	} else {
	$port_override = $postgresql::server::port
	}

if $port {
  $port_override = $port
} elsif 'PGPORT' in $connect_settings {
  $port_override = undef
} else {
  $port_override = $postgresql::server::port
}

Here the local $port parameter is preferred over $connect_settings. The problem is that we now cannot set a default in the resource for $port. The default is hardcoded to $postgresql::server::port. This becomes. Other classes handle it in a different way:

puppetlabs-postgresql/manifests/server/database.pp

Lines 41 to 46 in 93386b4

	# If the connection settings do not contain a port, then use the local server port
	if 'PGPORT' in $connect_settings {
	$port_override = undef
	} else {
	$port_override = $port
	}

if 'PGPORT' in $connect_settings {
  $port_override = undef
} else {
  $port_override = $port
}

Here $connct_settings is checked first. It defaults to an empty hash.
If PGPORT isn't in it, $port is used. The logic is shorter and
enables us to expose $port as a parameter with a default value. With
this approach users can decide if they pass $port or
$connect_settings.

At the moment the remote database support is broken because the logic to
parse $connect_settings isn't consistent. The goal of this PR is to
unify the logic and prefer $connect_settings if it's provided by the
user.

[bastelfreak]

I raised this to explain the current situation. This PR doesn't solve all the problems. If we agree on preferring $connect_settings I will update this PR and fix the other code pieces.

Edit: I updated all related code pieces.

[Ramesh7]

LGTM