[pgAdmin4][Patch]: Dependecies/Dependents functionality

Hi All

I have implemented the logic to show Dependencies/Dependents when user
click on browser nodes. Attached is the patch file, please review it and if
it looks good then please commit it.

I have also added this support in "Database" , "Tablespace" and "Role" as
this nodes are already been committed. Following is the information about
how to add the support in other nodes

*Add following lines of code in** <your module>.js*

- Add *hasDepends: true *in your file just like we have added *hasSQL*.

*Add following lines of code in <your module>.__init__.py*

"from pgadmin.browser.server_groups.servers.depends import
get_dependencies, get_dependents" to import the functions.

Implement the dependents and dependencies function like below. Pass the
appropriate node id and the name of the node to the functions
"get_dependents" and "get_dependencies"

@check_precondition
def dependents(self, gid, sid, did, lid):
"""
This function get the dependents and return ajax response
for the language node.

Args:
gid: Server Group ID
sid: Server ID
did: Database ID
lid: Language ID
"""
dependents_result = get_dependents(self.conn, lid, 'language')
return ajax_response(
response=dependents_result,
status=200
)

@check_precondition
def dependencies(self, gid, sid, did, lid):
"""
This function get the dependencies and return ajax response
for the language node.

Args:
gid: Server Group ID
sid: Server ID
did: Database ID
lid: Language ID
"""
dependencies_result = get_dependencies(self.conn, lid, 'language')
return ajax_response(
response=dependencies_result,
status=200
)

--
*Akshay Joshi*
*Principal Software Engineer *

*Phone: +91 20-3058-9517Mobile: +91 976-788-8246*