Change Default Certificate Hashing Algorithm to SHA-256

[hisanhunais]

Purpose

This PR changes the default certificate hashing algorithm to SHA-256 instead of SHA-1.

The following flows are affected due to this change.

1. The certificate hashing algorithm used in generating API keys will now use SHA-256 as the hashing algorithm

2. The certificate hashing algorithm used in generating backend JWTs for JWT and Opaque token SPs will now use SHA-256 as the default hashing algorithm. A config is provided to use SHA-1 as follows.

api-manager.xml.j2

<JWTConfiguration>
    ......
    <!-- Specifies whether to use SHA-1 algorithm to generate the certificate thumbprint -->
    <UseSHA1Hash>{{apim.jwt.use_sha1_hash}}</UseSHA1Hash>
    ......
</JWTConfiguration>

To use SHA-1 instead of SHA-256, the following has to be added to the deployment.toml.

deployment.toml

[apim.jwt]
enable = true
use_sha1_hash = false

• The PR [1] has to be merged after merging this PR to fix the integration test failures

[1] wso2/product-apim#13455

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 13 lines in your changes are missing coverage. Please review.

Project coverage is 41.62%. Comparing base (9471b04) to head (d2a9555).
Report is 11 commits behind head on master.

Files	Patch %	Lines
...apimgt/common/gateway/dto/JWTConfigurationDto.java	20.00%	4 Missing ⚠️
...o2/carbon/apimgt/impl/APIManagerConfiguration.java	0.00%	4 Missing ⚠️
...wtgenerator/AbstractAPIMgtGatewayJWTGenerator.java	0.00%	2 Missing ⚠️
...rbon/apimgt/keymgt/token/AbstractJWTGenerator.java	71.42%	2 Missing ⚠️
...so2/carbon/apimgt/common/gateway/util/JWTUtil.java	83.33%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #12365      +/-   ##
============================================
+ Coverage     36.35%   41.62%   +5.26%     
- Complexity        0     3487    +3487     
============================================
  Files          1861     1867       +6     
  Lines        137447   137934     +487     
  Branches      19867    19940      +73     
============================================
+ Hits          49967    57411    +7444     
+ Misses        80977    73576    -7401     
- Partials       6503     6947     +444     

Flag	Coverage Δ
integration_tests	35.10% <11.53%> (+7.11%)	⬆️
unit_tests	20.05% <38.46%> (-0.04%)	⬇️

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