Bump omniauth from 1.9.1 to 2.1.1

Bumps [omniauth](https://github.com/omniauth/omniauth) from 1.9.1 to 2.1.1.
- [Release notes](https://github.com/omniauth/omniauth/releases)
- [Commits](omniauth/omniauth@v1.9.1...v2.1.1)

---
updated-dependencies:
- dependency-name: omniauth
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -147,9 +147,10 @@ GEM
       multi_json (~> 1.3)
       multi_xml (~> 0.5)
       rack (>= 1.2, < 4)
-    omniauth (1.9.1)
+    omniauth (2.1.1)
       hashie (>= 3.4.6)
-      rack (>= 1.6.2, < 3)
+      rack (>= 2.2.3)
+      rack-protection
     omniauth-oauth2 (1.7.3)
       oauth2 (>= 1.4, < 3)
       omniauth (>= 1.9, < 3)
@@ -162,6 +163,8 @@ GEM
       nio4r (~> 2.0)
     racc (1.6.2)
     rack (2.2.6.3)
+    rack-protection (3.0.5)
+      rack
     rack-test (0.6.3)
       rack (>= 1.0)
     rails (5.0.7.2)