fix(loginresultparams): export all fields such that login provider im…

[ale8k]

Due to a mistake in the initial implementation of LoginProviders, the fields were left unexported. This disallows the capability of creating your own LoginProvider to Juju. The specific case here is a JWT login provider which is specific to JIMM and as such we wish to implement the provider in JIMM.

Checklist

• Code style: imports ordered, good names, simple structure, etc
• Comments saying why design decisions were made
• Go unit tests, with comments saying what you're testing
• Integration tests, with comments saying what you're testing
• doc.go added or updated in changed packages

QA steps

Documentation changes

Links

Launchpad bug: https://bugs.launchpad.net/juju/+bug/

Jira card: JUJU-

[wallyworld]

/build

[wallyworld]

I'm surprised there was no test fallout. That implies we have insufficient unit test coverage for these login providers. In fact, this code

func (s *tryInOrderLoginProviderSuite) Test(c *gc.C) {
	p1 := &mockLoginProvider{err: errors.New("provider 1 error")}
	p2 := &mockLoginProvider{err: errors.New("provider 2 error")}
	p3 := &mockLoginProvider{}

	lp := api.NewTryInOrderLoginProvider(p1, p2)
	_, err := lp.Login(context.Background(), nil)
	c.Assert(err, gc.ErrorMatches, "provider 2 error")

	lp = api.NewTryInOrderLoginProvider(p1, p2, p3)
	_, err = lp.Login(context.Background(), nil)
	c.Assert(err, jc.ErrorIsNil)
}

type mockLoginProvider struct {
	err error
}

func (p *mockLoginProvider) Login(ctx context.Context, caller base.APICaller) (*api.LoginResultParams, error) {
	return &api.LoginResultParams{}, p.err
}

should be updated to improve the test. Specifically this bit

	_, err = lp.Login(context.Background(), nil)
	c.Assert(err, jc.ErrorIsNil)
	
	```
should  test the returned value for a populated result struct.