Database provisioning interface enhancement

[Vonng]

Upgrade database creation interface to support complete features.

Current interface:

pg_databases:                       # create a business database 'meta'
  - name: meta
    schemas: [meta]                 # create extra schema named 'meta'
    extensions: [{name: postgis}]   # create extra extension postgis
    parameters:                     # overwrite database meta's default search_path
      search_path: public, monitor

Proposed interface

Which include complete customizable options for postgres database.

pg_databases:
  - name: meta                      # name is the only required field for a database
    owner: postgres                 # optional, database owner
    template: template1             # optional, template1 by default
    encoding: UTF8                  # optional, UTF8 by default
    locale: C                       # optional, C by default
    allowconn: true                 # optional, true by default, false disable connect at all
    revokeconn: false               # optional, false by default, true revoke connect from public # (only default user and owner have connect privilege on database)
    tablespace: pg_default          # optional, 'pg_default' is the default tablespace
    connlimit: -1                   # optional, connection limit, -1 or none disable limit (default)
    extensions:                     # optional, extension name and where to create
      - {name: postgis, schema: public}
    parameters:                     # optional, extra parameters with ALTER DATABASE
      enable_partitionwise_join: true
    pgbouncer: true                 # optional, add this database to pgbouncer list? true by default
    comment: pigsty meta database   # optional, comment string for database