Added docs and fix for ref grant in service import case

[tanujd11]

What type of PR is this?

What this PR does / why we need it:
Adds docs for the Multicluster services service import.
A fix is added for service import working with reference grant.
Which issue(s) this PR fixes:

Fixes #

[codecov]

Codecov Report

Merging #1852 (3d28e04) into main (f30dc6a) will increase coverage by 0.09%.
Report is 1 commits behind head on main.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main    #1852      +/-   ##
==========================================
+ Coverage   65.29%   65.39%   +0.09%     
==========================================
  Files          86       86              
  Lines       12526    12526              
==========================================
+ Hits         8179     8191      +12     
+ Misses       3828     3818      -10     
+ Partials      519      517       -2     

Files Changed	Coverage Δ
internal/provider/kubernetes/routes.go	43.72% <0.00%> (ø)

... and 2 files with indirect coverage changes

[Xunzhuo]

Thanks for a demo and also the fix : ) It worked for me.

[zirain]

/retest

[zirain]

/retest

seems like a github issue

[zirain]

/retest

[Xunzhuo]

@zirain just a code patch