Error message is not surfaced for error on saving a content block in grant editor

[goravseth]

OVERVIEW

When editing a grant application, if there is an error saving a section, I want to see what the error message is so I can resolve the error without losing my work.

Currently, if there is an error, the only thing that displays is "Section" in the error alert modal. In the dev console I can see an alert that says "Attribute 'message' should have a string value."

ACCEPTANCE CRITERIA
I triggered an error by pasting lorem ipsum to exceed the description length limit of 32k characters.

OUT OF SCOPE

BACKGROUND/REFERENCE

[iandrosov]

This issue was bit more complex than just error messages. No APex changes were needed but LWC JS code + HTML had be be major code changes.
Root Cuase is Apex DML exceptions defaults to relatively complex JSON response. Our LWC design was assuming text string error messages and was not able to parse just display red error box.

This is example JSON
{
"status": 500,
"body": {
"fieldErrors": {
"Text_Block__c": [
{
"statusCode": "STRING_TOO_LONG",
"message": "Text Block: data value too large: Lorem ipsum dolor sit amet, consectetur adipiscing mole... (max length=32768)"
}
]
},
"pageErrors": [],
"index": null,
"duplicateResults": []
},
"headers": {},
"ok": false,
"statusText": "Server Error",
"errorType": "fetchResponse"
};