Set the type of Bookmark.Port to int

We know that a port is a number. Lets enforce that
rule at type level by setting it so.

This commit also adjusts test funcs and helper data
to fit Port's new int type.

data/bookmark.toml

@@ -1,5 +1,5 @@
 host = "localhost"
-port = "5432"
+port = 5432
 user = "postgres"
 database = "mydatabase"
 ssl = "disable"

data/invalid_port.toml

@@ -1,5 +0,0 @@
-host = "localhost"
-port = 5432
-user = "postgres"
-database = "mydatabase"
-ssl = "disable"