Add max_failover_replication_time_lag configuration with constraints (

#938)

* Add `max_failover_replication_time_lag` configuration with constraints

- Set description for `max_failover_replication_time_lag`
- Define value constraints (min: 10, max: 9223372036854776000)
- Provide default (60) and example (4) values

* example should be within the range

* Update specification/resources/databases/models/advanced_config/postgres_advanced_config.yml

Co-authored-by: Andrew Starr-Bochicchio <andrewsomething@users.noreply.github.com>

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Co-authored-by: v.sharma <v.sharma@digitalocean.com>
Co-authored-by: Andrew Starr-Bochicchio <andrewsomething@users.noreply.github.com>

specification/resources/databases/models/advanced_config/postgres_advanced_config.yml

@@ -407,3 +407,10 @@ properties:
       Enable the pg_stat_monitor extension. <b>Enabling this extension will cause the cluster to be restarted.</b> When this extension is enabled, pg_stat_statements results for utility commands are unreliable.
     type: boolean
     example: false
+  max_failover_replication_time_lag:
+    description: >-
+      Number of seconds of master unavailability before triggering database failover to standby. The default value is 60.
+    type: integer
+    minimum: 10
+    maximum: 9223372036854776000
+    example: 50