Test social media post sharing via LinkedIn for an organization page

Currently, sharing social media posts through LinkedIn has been tested manually for a user profile. It could not be tested for an organization LinkedIn page due to lack of permissions to do so.
The code is written, keeping in mind, the organization page.

Hence, the piece of code needs to be tested for an organization page when LinkedIn allows us to have those permissions.

Reference to the API endpoint which is used is provided here https://docs.microsoft.com/en-us/linkedin/marketing/integrations/community-management/shares/ugc-post-api#create-ugc-posts

The post data needed to be sent with UGC(User Generated Content) API is similar to

```
post_data = {
'author': 'urn:li:organization:5590506',
'lifecycleState': 'PUBLISHED',
'specificContent': {
'com.linkedin.ugc.ShareContent': {
'shareCommentary': {
'text': post.text
},
'shareMediaCategory': 'NONE'
},
},
'visibility': {
'com.linkedin.ugc.MemberNetworkVisibility': 'PUBLIC'
},
}
```
However it is tested for `author` value as `urn:li:person:Yk8347` i.e. for a person and not for an organization.
The line within code that corresponds to this code change is https://github.com/CuriousLearner/nexus/pull/26/files#diff-7c07be7ecf752ba7bae9810c4d28c85cR80

Start at the code change shown in pull request #26, around the referenced line, and review the LinkedIn UGC Post API documentation. Test sharing with an organization author such as urn:li:organization:5590506 once the required LinkedIn permissions are available; done means the organization-page post is successfully published.

Written by the indexing model from the issue text.