Update Copyright headers

[owaiskazi19]

Signed-off-by: Owais Kazi owaiskazi19@gmail.com

Description

Updated copyright headers

Issues Resolved

#152

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[gaiksaya]

Thanks for taking care of this.

[owaiskazi19]

As mentioned here #152 (comment). Files like this should only have

# Copyright OpenSearch Contributors
# SPDX-License-Identifier: Apache-2.0

Can someone check here if the header is correct? Just wanted to confirm once

[gaiksaya]

@bbarani @peterzhuamazon can you verify. Looks like the second one is for For files that contain attribution to an external project

[bbarani]

Informed Miki to verify once as well

[bbarani]

Lets follow this rule,
First Remove the amazon header

1. • if there is no header left, use the 2-liner
2. • If there are other headers, use the long one

[peterzhuamazon]

This is the one that I use and confirmed by Open Source Team:

# SPDX-License-Identifier: Apache-2.0
#
# The OpenSearch Contributors require contributions made to
# this file be licensed under the Apache-2.0 license or a
# compatible open source license.

[owaiskazi19]

Looks like all the plugins teams have followed

# Copyright OpenSearch Contributors
# SPDX-License-Identifier: Apache-2.0

I would suggest let's have the same for consistency and as mentioned by Miki over here #152 (comment)