fix!: update Add/Remove due to 'username' argument being deprecated

[t-junjie]

BREAKING CHANGE: Replace 'username' argument with 'accountID'
Refer to: https://developer.atlassian.com/cloud/jira/platform/deprecation-notice-user-privacy-api-migration-guide/

Modify Group struct fields to reflect different fields returned by the API and documented JIRA API URLs to match the JIRA docs

Description

Please describe what does this Pull Request fix or add?

• The What: Update documented JIRA API URLs and modify Group struct & Add/Remove to match the JIRA docs
• The Why: The Add/Remove methods will fail upon being called now as they try to add or remove a user from group using their username, which is now deprecated. This update allows us to use these methods with the latest JIRA API.
• Type of change: Bugfix
• Breaking change: Yes, users will have to use accountid instead of username as argument to the abovementioned methods.
• Related to an issue: NA
• Jira Version + Type: Jira Cloud

Example:

Let us know how users can use or test this functionality.

// Add
group, resp, err := testClient.Group.Add("default", "000000000000000000000000");

// Remove
resp, err := testClient.Group.Remove("default", "000000000000000000000000"); 

Checklist

• Unit or Integration tests added
  • Good Path
  • Error Path
• Commits follow conventions described here:
  • Conventional Commits 1.0.0
  • The seven rules of a great Git commit message
• Commits are squashed such that
  • There is 1 commit per isolated change
• I've not made extraneous commits/changes that are unrelated to my change.

[andygrunwald]

Hey,

I am very sorry that this pull request has been open for a long time with no final feedback or merge/decline. We work on this project in our spare time, and sometimes, other priorities take over. This is the typical open source dilemma.

However, there is news: We are kicking off v2 of this library 🚀

To provide visibility, we created the Road to v2 Milestone and calling for your feedback in #489

The development will take some time; however, I hope you can benefit from the changes.
If you seek priority development for your pull request + you like to sponsor it, please contact me.

What does this mean for my pull request?

We will work on this pull request indirectly.
We might merge it during the development or pull parts of it into the new version.
This means that during the development phase, we aim to tackle it.
Maybe in a different way like it is currently handled.
Please understand that this will take a while because we are running this in our spare time.

Final words

Thanks for using and contributing to this library.
If there is anything else you would like to tell us, let us know!

[andygrunwald]

Thanks again @t-junjie for this Pull Request.
In the meantime, I did several changes in the library already.
Thats why I was not able to re-use your commits one by one.

I re-used your code as much as I could and re-implemented it in #589

I attributed the commit to you.
Thanks again!