Use context in new requests

[argenta-quanto]

In some methods the code below do not use the context passed thought the method:
ex:

func (p *Provider) UserInfo(ctx context.Context, tokenSource oauth2.TokenSource) (*UserInfo, error) {
	...
	if p.userInfoURL == "" {
		return nil, errors.New("oidc: user info endpoint is not supported by this provider")
	}

	req, err := http.NewRequest("GET", p.userInfoURL, nil)
	...

There is something that create some kind of risk in using :
req, err := http.NewRequestWithContext(ctx, "GET", p.userInfoURL, nil)

?

Thanks.

[argenta-quanto]

Made a PR:

#363

[ericchiang]

Can you take a look at #364?

[argenta-quanto]

Can you take a look at #364?

Yes, this is what I need.
Thanks.