Adding Feed Item into a Chatter Feed of Opportunity (source) object for a new Grant Record (Target)

gistfile1.java

Opportunity opty = new Opportunity(Id = '006i000000A0T3t');
Grant_Management__c grd = new Grant_Management__c(Name = 'Test 123');
insert grd;
 
ConnectApi.FeedItemInput input = new ConnectApi.FeedItemInput();
ConnectApi.MessageBodyInput messageInput = new ConnectApi.MessageBodyInput();
ConnectApi.TextSegmentInput textSegment;
ConnectApi.LinkSegmentInput linkSegment;
    
messageInput.messageSegments = new List<ConnectApi.MessageSegmentInput>();
 
textSegment = new ConnectApi.TextSegmentInput();
textSegment.text = ' New Grant Record Created: ';
textSegment.text += ' \n ';
messageInput.messageSegments.add(textSegment);
 
linkSegment = new ConnectApi.LinkSegmentInput();
linkSegment.URL = URL.getSalesforceBaseUrl().toExternalForm() + '/' + grd.Id; 
        
messageInput.messageSegments.add(linkSegment);
input.body = messageInput;
 
ConnectApi.FeedItem feedItemRep = ConnectApi.ChatterFeeds.postFeedItem(null, ConnectApi.FeedType.Record, opty.Id, input, null);