feat: update emails for self-signer (#1108)

## Description

Updated the email content based on whether the document owner is a
recipient or not.

If the document owner is a recipient (self-signer):
* the email subject will be `Please view/sign/approve your document`
* the email header will be `Please view/sign/approve your document
"<your-doc-title>"`
* the email content will be `You have initiated the document
"<your-doc-title>" that requires you to view/sign/approve it.`

Otherwise:
* the email subject will be `Please view/sign/approve this document`
* the email header will be `<doc-owner> has invited you to
view/sign/approve "<doc-title>"`
* the email content will be `<doc-owner> has invited you to
view/sign/approve the document "<doc-title>".`


## Related Issue

Related to #1091 

## Testing Performed

Tested the feature with a different number of recipients (including and
excluding the document owner - self-signer). Tested both the sending and
resending functionality.

## Checklist

- [x] I have tested these changes locally and they work as expected.
- [ ] I have added/updated tests that prove the effectiveness of these
changes.
- [ ] I have updated the documentation to reflect these changes, if
applicable.
- [x] I have followed the project's coding style guidelines.
- [ ] I have addressed the code review feedback from the previous
submission, if applicable.

## UI Screenshots

![CleanShot 2024-04-18 at 12 26
11@2x](https://github.com/documenso/documenso/assets/25515812/ca80f625-befb-4cbc-a541-f2186379d2e8)
![CleanShot 2024-04-18 at 12 27
40@2x](https://github.com/documenso/documenso/assets/25515812/8bcbb6fc-ba98-4fa1-8538-2d062febd27b)
![CleanShot 2024-04-18 at 12 27
53@2x](https://github.com/documenso/documenso/assets/25515812/25d77d98-b5ec-4270-8ffa-43774fe70526)
![CleanShot 2024-04-18 at 12 30
00@2x](https://github.com/documenso/documenso/assets/25515812/a90bb8e3-3ea8-42ff-9971-559b3e81ae6f)


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

## Summary by CodeRabbit

- **New Features**
- Enhanced the document invitation components to support scenarios where
the recipient is also the sender, providing customized email content and
subject lines.
- Introduced new properties in email templates to improve clarity and
relevance based on the user's role in the document signing process.

- **Refactor**
- Updated components to use a more flexible `headerContent` property for
displaying invitation headers, replacing previous individual inviter
details.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/email/template-components/template-document-invite.tsx

@@ -11,6 +11,7 @@ export interface TemplateDocumentInviteProps {
   signDocumentLink: string;
   assetBaseUrl: string;
   role: RecipientRole;
+  selfSigner: boolean;
 }
 
 export const TemplateDocumentInvite = ({
@@ -19,6 +20,7 @@ export const TemplateDocumentInvite = ({
   signDocumentLink,
   assetBaseUrl,
   role,
+  selfSigner,
 }: TemplateDocumentInviteProps) => {
   const { actionVerb, progressiveVerb } = RECIPIENT_ROLES_DESCRIPTION[role];
 
@@ -28,8 +30,19 @@ export const TemplateDocumentInvite = ({
 
       <Section>
         <Text className="text-primary mx-auto mb-0 max-w-[80%] text-center text-lg font-semibold">
-          {inviterName} has invited you to {actionVerb.toLowerCase()}
-          <br />"{documentName}"
+          {selfSigner ? (
+            <>
+              {`Please ${actionVerb.toLowerCase()} your document`}
+              <br />
+              {`"${documentName}"`}
+            </>
+          ) : (
+            <>
+              {`${inviterName} has invited you to ${actionVerb.toLowerCase()}`}
+              <br />
+              {`"${documentName}"`}
+            </>
+          )}
         </Text>
 
         <Text className="my-1 text-center text-base text-slate-400">