fix(revocation): avoid revoking expired tokens and fail gracefully (#95)

Fixes #72

If an Actions job is long enough, more than an hour can pass between
creating and revoking the App token in the post-job clean up step. Since
the token itself is used to authenticate with the revoke API, an expired
token will fail to be revoked.

This PR saves the token expiration in the actions state and uses that in
the post step to determine if the token can be revoked. I've also added
error handling to the revoke token API call, as it's unlikely that users
would want their job to fail if the token can't be revoked.

tests/snapshots/index.js.md

@@ -69,7 +69,9 @@ Generated by [AVA](https://avajs.dev).
     ::add-mask::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
     ␊
     ::set-output name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
-    ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a`
+    ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
+    ␊
+    ::set-output name=expiresAt::2016-07-11T22:14:10Z`
 
 ## main-token-get-owner-set-repo-set-to-many.test.js
 
@@ -83,7 +85,9 @@ Generated by [AVA](https://avajs.dev).
     ::add-mask::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
     ␊
     ::set-output name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
-    ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a`
+    ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
+    ␊
+    ::set-output name=expiresAt::2016-07-11T22:14:10Z`
 
 ## main-token-get-owner-set-repo-set-to-one.test.js
 
@@ -97,7 +101,9 @@ Generated by [AVA](https://avajs.dev).
     ::add-mask::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
     ␊
     ::set-output name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
-    ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a`
+    ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
+    ␊
+    ::set-output name=expiresAt::2016-07-11T22:14:10Z`
 
 ## main-token-get-owner-set-to-org-repo-unset.test.js
 
@@ -111,7 +117,9 @@ Generated by [AVA](https://avajs.dev).
     ::add-mask::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
     ␊
     ::set-output name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
-    ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a`
+    ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
+    ␊
+    ::set-output name=expiresAt::2016-07-11T22:14:10Z`
 
 ## main-token-get-owner-set-to-user-fail-response.test.js
 
@@ -126,7 +134,9 @@ Generated by [AVA](https://avajs.dev).
     ::add-mask::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
     ␊
     ::set-output name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
-    ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a`
+    ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
+    ␊
+    ::set-output name=expiresAt::2016-07-11T22:14:10Z`
 
 ## main-token-get-owner-set-to-user-repo-unset.test.js
 
@@ -140,7 +150,9 @@ Generated by [AVA](https://avajs.dev).
     ::add-mask::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
     ␊
     ::set-output name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
-    ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a`
+    ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
+    ␊
+    ::set-output name=expiresAt::2016-07-11T22:14:10Z`
 
 ## main-token-get-owner-unset-repo-set.test.js
 
@@ -154,7 +166,9 @@ Generated by [AVA](https://avajs.dev).
     ::add-mask::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
     ␊
     ::set-output name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
-    ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a`
+    ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
+    ␊
+    ::set-output name=expiresAt::2016-07-11T22:14:10Z`
 
 ## main-token-get-owner-unset-repo-unset.test.js
 
@@ -168,7 +182,29 @@ Generated by [AVA](https://avajs.dev).
     ::add-mask::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
     ␊
     ::set-output name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
-    ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a`
+    ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
+    ␊
+    ::set-output name=expiresAt::2016-07-11T22:14:10Z`
+
+## post-revoke-token-fail-response.test.js
+
+> stderr
+
+    ''
+
+> stdout
+
+    '::warning::Token revocation failed: '
+
+## post-token-expired.test.js
+
+> stderr
+
+    ''
+
+> stdout
+
+    'Token expired, skipping token revocation'
 
 ## post-token-set.test.js