Restrict on-call to certain times during rotations

What does this MR do?

This adds the ability to restrict an oncall rotation (and it's shift) to a time active period (i.e between the hours of 8am and 5pm).

To allow this we have:

• Added two more columns to incident_management_oncall_rotations; active_period_start, active_period_end.
• Added two fields to the GraphQL mutation to create Oncall Rotations

DB Migrations:

Up:

== 20210201034649 AddActivePeriodsToOnCallRotations: migrating ================
-- add_column(:incident_management_oncall_rotations, :active_period_start, :text, {:null=>true})
   -> 0.0032s
-- add_column(:incident_management_oncall_rotations, :active_period_end, :text, {:null=>true})
   -> 0.0004s
== 20210201034649 AddActivePeriodsToOnCallRotations: migrated (0.0037s) =======

== 20210205051437 AddTextLimitToRotationActivePeriodsColumns: migrating =======
-- transaction_open?()
   -> 0.0000s
-- current_schema()
   -> 0.0002s
-- execute("ALTER TABLE incident_management_oncall_rotations\nADD CONSTRAINT check_30b841c47f\nCHECK ( char_length(active_period_start) <= 5 )\nNOT VALID;\n")
   -> 0.0038s
-- current_schema()
   -> 0.0002s
-- execute("SET statement_timeout TO 0")
   -> 0.0001s
-- execute("ALTER TABLE incident_management_oncall_rotations VALIDATE CONSTRAINT check_30b841c47f;")
   -> 0.0014s
-- execute("RESET ALL")
   -> 0.0001s
-- transaction_open?()
   -> 0.0000s
-- current_schema()
   -> 0.0002s
-- execute("ALTER TABLE incident_management_oncall_rotations\nADD CONSTRAINT check_10f7ba666c\nCHECK ( char_length(active_period_end) <= 5 )\nNOT VALID;\n")
   -> 0.0006s
-- current_schema()
   -> 0.0001s
-- execute("ALTER TABLE incident_management_oncall_rotations VALIDATE CONSTRAINT check_10f7ba666c;")
   -> 0.0004s
== 20210205051437 AddTextLimitToRotationActivePeriodsColumns: migrated (0.0155s)

Down:

== 20210201034649 AddActivePeriodsToOnCallRotations: reverting ================
-- remove_column(:incident_management_oncall_rotations, :active_period_end, :text, {:null=>true})
   -> 0.0097s
-- remove_column(:incident_management_oncall_rotations, :active_period_start, :text, {:null=>true})
   -> 0.0003s
== 20210201034649 AddActivePeriodsToOnCallRotations: reverted (0.0129s) =======

== 20210205051437 AddTextLimitToRotationActivePeriodsColumns: reverting =======
-- execute("ALTER TABLE incident_management_oncall_rotations\nDROP CONSTRAINT IF EXISTS check_30b841c47f\n")
   -> 0.0004s
-- execute("ALTER TABLE incident_management_oncall_rotations\nDROP CONSTRAINT IF EXISTS check_10f7ba666c\n")
   -> 0.0002s
== 20210205051437 AddTextLimitToRotationActivePeriodsColumns: reverted (0.0075s)

GraphQL Query

Mutation

mutation newRotation($input: OncallRotationCreateInput!) {
  oncallRotationCreate(input: $input) {
    oncallRotation {
      id
      name
      startsAt
      length
      lengthUnit
      activePeriodStart
      activePeriodEnd
      participants {
        nodes {
          user {
            username
          }
          colorWeight
          colorPalette
        }
      }
    }
    errors
  }
}

Input

{
  "input": {
    "projectPath": "root/autodevops-deploy-test",
    "scheduleIid": "1",
    "name": "test rotation 6",
    "startsAt": {
      "date": "2021-02-01",
      "time": "08:00"
    },
    "rotationLength": {
      "length": 1,
      "unit": "DAYS"
    },
    "participants": [
      {
        "username": "root",
        "colorWeight": "WEIGHT_500",
        "colorPalette": "GREEN"
      }
    ],
    "activePeriod": {
      "from": "08:00",
      "to": "17:00"
    }
  }
}

Output

{
  "data": {
    "oncallRotationCreate": {
      "oncallRotation": {
        "id": "gid://gitlab/IncidentManagement::OncallRotation/20",
        "name": "test rotation 3",
        "startsAt": "2021-01-31T19:00:00Z",
        "length": 1,
        "lengthUnit": "DAYS",
        "activePeriodStart": "08:00",
        "activePeriodEnd": "17:00",
        "participants": {
          "nodes": [
            {
              "user": {
                "username": "root"
              },
              "colorWeight": "500",
              "colorPalette": "green"
            }
          ]
        }
      },
      "errors": []
    }
  }
}

</details>
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## Does this MR meet the acceptance criteria?

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Related to #262859