SearchService#searchPostByUrl breaks if the number of Posts is less than a full page

[alter-kaker]

This method fails with a IndexOutOfBoundsException if the number of posts returned in the CrossPost.posts field is less than needed to fill the current requested page.

For example:

• 0 Post objects returned for page=0, pageSize=1
• 1 Post objects returned for page=0, pageSize=2
• 3 Post objects returned for page=1, pageSize=2
• 4 Post objects returned for page=2, pageSize=4

[alter-kaker]

See disabled tests in #423

[Pdzly]

The issue on hand here is that we expect a page range from 1-open end. I will fix it by clamping that value in the service.

And add some java doc to there when i am already there

This should be the same issue with the other functions too.
Because there should not be a 0 acceptable from the api and thus this issue never occured.