Batch of fixes

[ActiveChooN]

Motivation and context

Added Open task button for task creation notification
Added links to header buttons. Related to #1419
Fixed #2015
Fixed #1054

How has this been tested?

Manually

Checklist

• I submit my changes into the develop branch
• I have added description of my changes into CHANGELOG file
  - [ ] I have updated the documentation accordingly
  - [ ] I have added tests to cover my changes
• I have linked related issues (read github docs)
• I have increased versions of npm packages if it is necessary (cvat-canvas,
  cvat-core, cvat-data and cvat-ui)

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.
• I have updated the license header for each file (see an example below)

# Copyright (C) 2020 Intel Corporation
#
# SPDX-License-Identifier: MIT

[ActiveChooN]

@azhavoro, have an issue with CI, could you look at it?

[azhavoro]

@azhavoro, have an issue with CI, could you look at it?

@ActiveChooN The validate_labels method should return the validated value. I guess this is the reason for the failed CI tests.

[coveralls]

Pull Request Test Coverage Report for Build 6996

• 5 of 7 (71.43%) changed or added relevant lines in 1 file are covered.
• 182 unchanged lines in 7 files lost coverage.
• Overall coverage increased (+0.8%) to 69.721%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
cvat/apps/engine/serializers.py	5	7	71.43%

Files with Coverage Reduction	New Missed Lines	%
cvat/apps/engine/media_extractors.py	2	76.99%
datumaro/datumaro/components/algorithms/rise.py	5	90.7%
datumaro/datumaro/cli/main.py	11	0%
datumaro/datumaro/cli/util/init.py	15	27.59%
datumaro/datumaro/components/extractor.py	24	91.8%
datumaro/datumaro/components/operations.py	55	90.55%
datumaro/datumaro/components/project.py	70	80.0%

Totals
Change from base Build 6913:	0.8%
Covered Lines:	11725
Relevant Lines:	16363

---

💛 - Coveralls

[bsekachev]

@ActiveChooN

Looks like some of cypress tests have broken. Could you please look why?

[dvkruchinin]

@ActiveChooN

Looks like some of cypress tests have broken. Could you please look why?

I'll answer if you don't mind.
Currently, cypress is looking for a button with the value "tasks" to go to the list of tasks after creating an annotation task.
The button looks like this

<button value="tasks" type="button" class="ant-btn cvat-header-button ant-btn-link"><span>Tasks</span></button>

In this PR the button becomes a link

<a value="tasks" href="/tasks?page=1" class="ant-btn cvat-header-button ant-btn-link"><span>Tasks</span></a>

This error can be resolved by changing line 37 in the file tests/cypress/support/commands.js
from

cy.get('button[value="tasks"]').click()

to

cy.get('[value="tasks"]').click()

[ActiveChooN]

@dvkruchinin, thanks a lot.