Define modules

Are you filing an issue about iOS 12?
You can find preliminary support for iOS 12 in the (ios12beta branch)[https://github.com/openid/AppAuth-iOS/tree/ios12beta] and background information in (the associated pull request)[https://github.com/openid/AppAuth-iOS/pull/246]. Please review these materials before filing iOS 12 issues. Thanks.

Is your feature request related to a problem? Please describe.
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Yes this is my case, I have embedded AppAuth in my swift pod framework, but when I try to use my lib via pod in a project I cannot even succeed in "pod install" it is always failing with error:

[!] The following Swift pods cannot yet be integrated as static libraries:

The Swift pod Auth depends upon AppAuth, which does not define modules. To opt into those targets generating module maps (which is necessary to import them from Swift when building as static libraries), you may set use_modular_headers! globally in your Podfile, or specify :modular_headers => true for particular dependencies.

As far as I have already tried to go on with use_modular_headers but with no success because in that case it is conflicting with
other pods, though I am using pods 1.9.3. I need a solution.

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I would like you to add support for modules.

Describe alternatives you've considered
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Additional context
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Start by reproducing the reported pod install failure using the Auth and AppAuth pods with static-library integration, then inspect the Podfile settings for use_modular_headers and modular_headers. Done means AppAuth provides module support so the dependency can be imported by the Swift Auth pod without the reported integration error or the conflicting global setting.