enhancement: improve text clearing process in email partitioning (#3422)

### Summary
Currently, the email partitioner removes only `=\n` characters during
the clearing process. However, email content sometimes contains `=\r\n`
characters, especially when read from file-like objects such as
`SpooledTemporaryFile` (the file type used in our API). This PR updates
the email partitioner to remove both `=\n` and `=\r\n` characters during
the clearing process.

### Testing

```
filename = "example-docs/eml/family-day.eml"

elements = partition_email(
    filename=filename,
)
print(f"From filename: {elements[3].text}")

with open(filename, "rb") as test_file:
    spooled_temp_file = tempfile.SpooledTemporaryFile()
    spooled_temp_file.write(test_file.read())
    spooled_temp_file.seek(0)
    elements = partition_email(file=spooled_temp_file)
    print(f"From spooled_temp_file: {elements[3].text}")
```

**Results:**
- on `main`
```
From filename: Make sure to RSVP!
From spooled_temp_file: Make sure to = RSVP!
```
- on `PR`
```
From filename: Make sure to RSVP!
From spooled_temp_file: Make sure to RSVP!
```

CHANGELOG.md

@@ -1,7 +1,8 @@
-## 0.15.0-dev16
+## 0.15.0
 
 ### Enhancements
 
+* **Improve text clearing process in email partitioning.** Updated the email partitioner to remove both `=\n` and `=\r\n` characters during the clearing process. Previously, only `=\n` characters were removed.   
 * **Bump unstructured.paddleocr to 2.8.0.1.**
 * **Refine HTML parser to accommodate block element nested in phrasing.** HTML parser no longer raises on a block element (e.g. `<p>`, `<div>`) nested inside a phrasing element (e.g. `<strong>` or `<cite>`). Instead it breaks the phrasing run (and therefore element) at the block-item start and begins a new phrasing run after the block-item. This is consistent with how the browser determines element boundaries in this situation.
 * **Install rewritten HTML parser to fix 12 existing bugs and provide headroom for refinement and growth.** A rewritten HTML parser resolves a collection of outstanding bugs with HTML partitioning and provides a firm foundation for further elaborating that important partitioner.

example-docs/eml/family-day.eml

@@ -0,0 +1,39 @@
+MIME-Version: 1.0
+Date: Wed, 21 Dec 2022 10:28:53 -0600
+Message-ID: <CAPgNNXQKR=o6AsOTr74VMrsDNhUJW0Keou9n3vLa2UO_Nv+tZw@mail.gmail.com>
+Subject: Family Day
+From: Mallori Harrell <mallori@unstructured.io>
+To: Mallori Harrell <mallori@unstructured.io>
+Content-Type: multipart/alternative; boundary="0000000000005c115405f0590ce4"
+
+--0000000000005c115405f0590ce4
+Content-Type: text/plain; charset="UTF-8"
+
+Hi All,
+
+Get excited for our first annual family day!
+
+There will be face painting, a petting zoo, funnel cake and more.
+
+Make sure to RSVP!
+
+Best.
+
+-- 
+Mallori Harrell
+Unstructured Technologies
+Data Scientist
+
+--0000000000005c115405f0590ce4
+Content-Type: text/html; charset="UTF-8"
+Content-Transfer-Encoding: quoted-printable
+
+<div dir=3D"ltr">Hi All,<div><br></div><div>Get excited for our first annua=
+l family day!=C2=A0</div><div><br></div><div>There will be face painting, =
+a petting zoo, funnel cake and more.</div><div><br></div><div>Make sure to =
+RSVP!</div><div><br></div><div>Best.<br clear=3D"all"><div><br></div>-- <br=
+><div dir=3D"ltr" class=3D"gmail_signature" data-smartmail=3D"gmail_signatu=
+re"><div dir=3D"ltr">Mallori Harrell<div>Unstructured Technologies<br><div>=
+Data Scientist</div><div><br></div></div></div></div></div></div>
+
+--0000000000005c115405f0590ce4--

test_unstructured/partition/test_email.py

@@ -2,6 +2,7 @@ import datetime
 import email
 import os
 import pathlib
+import tempfile
 
 import pytest
 
@@ -230,6 +231,17 @@ def test_partition_email_from_file_rb_default_encoding(filename, expected_output
         assert element.metadata.filename is None
 
 
+def test_partition_email_from_spooled_temp_file():
+    filename = example_doc_path("eml/family-day.eml")
+    with open(filename, "rb") as test_file:
+        spooled_temp_file = tempfile.SpooledTemporaryFile()
+        spooled_temp_file.write(test_file.read())
+        spooled_temp_file.seek(0)
+        elements = partition_email(file=spooled_temp_file)
+        assert len(elements) == 9
+        assert elements[3].text == "Make sure to RSVP!"
+
+
 def test_partition_email_from_text_file():
     filename = os.path.join(EXAMPLE_DOCS_DIRECTORY, "fake-email.txt")
     with open(filename) as f:

unstructured/__version__.py

@@ -1 +1 @@
-__version__ = "0.15.0-dev16"  # pragma: no cover
+__version__ = "0.15.0"  # pragma: no cover

unstructured/partition/email.py

@@ -416,8 +416,8 @@ def partition_email(
         #    <li>Item 1</li>=
         #    <li>Item 2<li>=
         # </ul>
-        list_content = content.split("=\n")
-        content = "".join(list_content)
+
+        content = content.replace("=\n", "").replace("=\r\n", "")
         elements = partition_html(
             text=content,
             include_metadata=False,