[TO] Added a new route and logic for assigning multiple server capabilities to a server

[rimashah25]

Closes: #7088

---

Which Traffic Control components are affected by this PR?

• Documentation
• Traffic Ops

What is the best way to verify this PR?

Using curl cmds test the new route with a list of server capabilities

• Success Assignment

curl -X PUT -k -H "Accept: application/json" --cookie "mojolicious=" --data @msc.json https://localhost:port/api/4.1/multiple_server_capabilities/106

{
	"alerts": [{
		"text": "Multiple Server Capabilities assigned to a server:106",
		"level": "success"
	}],
	"response": {
		"serverId": 106,
		"serverCapability": ["test", "disk"]
	}
}

• Trying to assign server capabilities for an unknown server

curl -X PUT -k -H "Accept: application/json" --cookie "mojolicious==" --data @msc.json https://localhost:port/api/4.1/multiple_server_capabilities/3

{
	"alerts": [{
		"text": "server 3 does not exist",
		"level": "error"
	}]
}

• Incorrect route

curl -X PUT -k -H "Accept: application/json" --cookie "mojolicious==" --data @msc.json https://localhost:port/api/4.0/multiple_server_capabilities/3

{
	"alerts": [{
		"text": "The requested path '/api/4.0/multiple_server_capabilities/3' does not exist.",
		"level": "error"
	}]
}

PR submission checklist

• This PR has tests
• This PR has documentation
• This PR has a CHANGELOG.md entry
• This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY (see the Apache Software Foundation's security guidelines for details)

[ocket8888]

Did you consider just adding the ability to submit an array of capabilities to server_server_capabilities instead of making an endpoint? If so, why did you decide against it?

[ocket8888]

The endpoint seems to work well from testing. Just a couple of minor comments.