Lock down institution data retrieval

[lchen-2101]

Have institution retrieval be tied to user email domain and / or associated lei

[jcadam14]

I created a story in filing-api cfpb/sbl-filing-api#105 where I comment it might be good to put in the commons repo a router that does the check for lei like I added to filing, so all our apis can reuse that router if needed. So might be something to discuss/think about for this, too.

[lchen-2101]

Yeap, some functionalities are shared between the two; the path-based ones will pretty much be the same. The part that doesn't quite fit both is the search / query-param based; also there's an "admin" type user that can do everything here that I'm thinking of preserving. Exploring using decorator instead of dependencies at the moment.