Store notification content as binary to support unicode

[darshanasbg]

Proposed changes in this pull request

$subject. Related to,

• https://github.com/wso2/product-is/issues/21235

When should this PR be merged

Immediate.

Follow up actions

Merge,

• https://github.com/wso2-extensions/identity-event-handler-notification/pull/280

And update product-is, to include both this and above PR to include in the same commit.

PS:

And update product-is, to include both this and above PR to include in the same commit.

Done with:

• https://github.com/wso2/product-is/pull/21775

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 40.79%. Comparing base (6ffda9f) to head (9786b7c). Report is 95 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #6120 +/- ## ========================================= Coverage 40.79% 40.79% + Complexity 14550 14541 -9 ========================================= Files 1772 1772 Lines 118320 118320 Branches 19266 19266 ========================================= Hits 48274 48274 Misses 62743 62743 Partials 7303 7303 ``` | [Flag](https://app.codecov.io/gh/wso2/carbon-identity-framework/pull/6120/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=wso2) | Coverage Δ | | |---|---|---| | [unit](https://app.codecov.io/gh/wso2/carbon-identity-framework/pull/6120/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=wso2) | `25.07% <ø> (+<0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=wso2#carryforward-flags-in-the-pull-request-comment) to find out more.

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