Auth: Allow expiration of API keys (#17678)

* Modify backend to allow expiration of API Keys

* Add middleware test for expired api keys

* Modify frontend to enable expiration of API Keys

* Fix frontend tests

* Fix migration and add index for `expires` field

* Add api key tests for database access

* Substitude time.Now() by a mock for test usage

* Front-end modifications

* Change input label to `Time to live`
* Change input behavior to comply with the other similar
* Add tooltip

* Modify AddApiKey api call response

Expiration should be *time.Time instead of string

* Present expiration date in the selected timezone

* Use kbn for transforming intervals to seconds

* Use `assert` library for tests

* Frontend fixes

Add checks for empty/undefined/null values

* Change expires column from datetime to integer

* Restrict api key duration input

It should be interval not number

* AddApiKey must complain if SecondsToLive is negative

* Declare ErrInvalidApiKeyExpiration

* Move configuration to auth section

* Update docs

* Eliminate alias for models in modified files

* Omit expiration from api response if empty

* Eliminate Goconvey from test file

* Fix test

Do not sleep, use mocked timeNow() instead

* Remove index for expires from api_key table

The index should be anyway on both org_id and expires fields.
However this commit eliminates completely the index for now
since not many rows are expected to be in this table.

* Use getTimeZone function

* Minor change in api key listing

The frontend should display a message instead of empty string
if the key does not expire.

docs/sources/http_api/auth.md

@@ -82,7 +82,8 @@ Content-Type: application/json
   {
     "id": 1,
     "name": "TestAdmin",
-    "role": "Admin"
+    "role": "Admin",
+    "expiration": "2019-06-26T10:52:03+03:00"
   }
 ]
 ```
@@ -101,7 +102,8 @@ Authorization: Bearer eyJrIjoiT0tTcG1pUlY2RnVKZTFVaDFsNFZXdE9ZWmNrMkZYbk
 
 {
   "name": "mykey",
-  "role": "Admin"
+  "role": "Admin",
+  "secondsToLive": 86400
 }
 ```
 
@@ -109,6 +111,12 @@ JSON Body schema:
 
 - **name** – The key name
 - **role** – Sets the access level/Grafana Role for the key. Can be one of the following values: `Viewer`, `Editor` or `Admin`.
+- **secondsToLive** – Sets the key expiration in seconds. It is optional. If it is a positive number an expiration date for the key is set. If it is null, zero or is omitted completely (unless `api_key_max_seconds_to_live` configuration option is set) the key will never expire.
+
+Error statuses:
+
+- **400** – `api_key_max_seconds_to_live` is set but no `secondsToLive` is specified or `secondsToLive` is greater than this value.
+- **500** – The key was unable to be stored in the database.
 
 **Example Response**: