Add missing tabs to org projects page (#22705) (#23412)

Backport #22705 by @yp05327

Fixes https://github.com/go-gitea/gitea/issues/22676

Context Data `IsOrganizationMember` and `IsOrganizationOwner` is used to
control the visibility of `people` and `team` tab.

2871ea0809/templates/org/menu.tmpl (L19-L40)

And because of the reuse of user projects page, User Context is changed
to Organization Context. But the value of `IsOrganizationMember` and
`IsOrganizationOwner` are not being given.

I reused func `HandleOrgAssignment` to add them to the ctx, but may have
some unnecessary variables, idk whether it is ok.

I found there is a missing `PageIsViewProjects` at create project page.

Co-authored-by: yp05327 <576951401@qq.com>

models/user/user.go

@@ -393,6 +393,11 @@ func (u *User) IsOrganization() bool {
 	return u.Type == UserTypeOrganization
 }
 
+// IsIndividual returns true if user is actually a individual user.
+func (u *User) IsIndividual() bool {
+	return u.Type == UserTypeIndividual
+}
+
 // DisplayName returns full name if it's not empty,
 // returns username otherwise.
 func (u *User) DisplayName() string {